Complete Walkthrough on How To Obtain 100% Completion

This is a check list of what you need to do to get 100%. This guide is also considering you've completed every mission at least once on normal.

1. Collect all XOF patches
2. Collect all Cassette Tapes
3. Unlock all trials, no this doesn't mean you have to complete them, just unlock.
4. S rank every mission on normal and hard.
5. Answer all the questions on the Deja Vu quizes correctly, both on normal and hard.
6. Rescue all POW's through out every mission. (including the two targets on the Renegade Threat mission)

So pretty much just work your way towards every achievement.

Remember to extract every POW around Chico's prison cell area.
It's recommended you complete these in the order the guide lists them.
The S rank part of the guide was the easiest way "I" found, may not be the same for you.

"B-but w-why are you making such an in depth guide about everything if that's all you needed to say / there are heaps of other guides out there???"

Because I'm bored sh|tless and got nothing better to do on a Sunday night.
The videos in this guide are by PowerPyx, go check him out. (https://www.youtube.com/user/PowerPyx/featured)

I don't know how many people read this guide now with the game being a few years old and the Metal Gear hype dead now, but please keep in mind this guide is worded incredibly poorly with some terrible grammar as I wrote this when I was only about 13 or 14 (too lazy to rework this guide since I doubt it'd be worth it). There's a much better worded 100% guide that's the second highest rated which might prove to be better.

Also. a few people mentioned some better strategies to certain parts of the guide so be sure to check out the comments.

These can only be obtained in the main Ground Zeroes mission. Also using your night vision makes this 10x easier. In total there are 9 XOF patches to collect, this will also unlock the Deja Vu and Jamais Vu missions. Just note the patches aren't seen in these screenshots since I've already obtained them.

As soon as you start, turn around and to your right it should be on the cliff.
On top of a pile of garbage towards the south side of the west refugee camp.
On top of one of the machines in the caged area towards the north end of the warehouse area, next to the helipad.
On top of the guard house next to the prison where Chico was being held..
From the guard house go towards the prison, the patch will be on the ground as soon as you walk in.
In a puddle between the two helipads.
In the drainage tunnel towards the north wall of the helipad, around where the armoury and the door leading into the admin building is.
On top of the air vent on top of the building in the east wing of the admin building (through the door I was talking about near patch 7). Jump onto the machine then onto the roof to get to it.
It's stuck in Biggu Bossu's pouch, just roll a bunch on the ground to get it.
Video Format

You should now have all XOF patches.

There are a total of 13 tapes you need, 7 of which are Chico tapes. Just note you can't see any of the tapes in these screenshots since I've already obtained them all.

Simply complete the "Intel Operative Rescue" mission on any difficulty. In the main Ground Zeroes mission, in the admin building watchtower.
In the main Ground Zeroes mission again, you'll automatically get it after getting Chico to the helicopter. In the Ground Zeroes mission once again, rescue the POW in the west refugee camp, straight ahead of you as soon as you start. You'll get it after completing the mission.
Ground Zeroes mission, inside the admin building area in an alleyway towards the boiler room straight ahead of you on a dumpster. THIS CAN ONLY BE OBTAINED BEFORE YOU MEET CHICO
In the "Eliminate the Renegade Threat" mission, inside the armory with the red door that is closest to where you start in the main mission.
Finally the last Chico tape, in the "Destroy the Anti-Air Emplacements" rescue the POW in the boiler room, he's in the same place Paz is in the main mission. You'll get it after completing the mission.
In the "Classified Intel Aquisition" mission, exact same place as the second Chico tape. Just ride the truck you start on into the admin building.
Same mission as before, in the boiler room there should be a shaved headed soldier standing there, he'll drop the tape after saying "Spit it out" twice while holding him up.
- In the main Ground Zeroes mission, located in the same cell as Chicos just the other door behind.
In the Deja Vu and Jamais Vu missions you get for obtaining all XOF patches. On a rock towards where you extract Chico in the GZ mission / where you start off in the Renegade Threat mission. Use your night vision to see it easier.
Just note you need to do this on both missions as they are separete tapes.
Complete every mission on hard, doesn't matter what rank you get.

Video format

By now you should have every tape there is,

Like I said in the first section you only need to unlock the trials, not complete all of them.

The best way to do this is complete the fastest tagging of all enemies trial (so tag every enemy on the map) on normal in every mission then complete every mission on hard, doesn't matter what rank you get or if you complete any trials.

For the fastest marking, make sure you don't kill anyone, look in every inch of the map even in places where you wouldn't think where they would be.

If you've been doing this guide in order and obtained the ZOE tape you should only have to complete the missions on hard once, if not chances are you'll have to do it twice.

So now it's time to S rank every mission on normal and hard. Normal shouldn't be too bad but hard... well yeah it can be hard, mainly the day time missions.

Things to keep in mind about your score.

-Killing people will deduct from your final score.
-Alerts will deduct from your final score as well.
-Restarting from the latest checkpoint will also deduct.
-Helicopters getting shot down deducts as well.
-Extracting POWs will add to your final score.
-The quicker you finish the mission, more points you will get for it.
-Disabling reflex mode also boosts your score.

Finishing the mission as fast as possible is one of the most important things as it will get you most points.

Not much to say about this one, just once you get to Chico extract every hostage in the cells around him to boost the score, extract Chico and go get Paz, extract her and you're done. Shouldn't be too hard.
You're going to want to only kill the two targets and no one else. Towards the helipad there will be a truck with a sniper rifle in the back, tranq the enemies around it and pick it up. To the west of the truck there will be a wooden tower, tranq the enemies around there as well and climb up the tower.

Look through your sniper to around the north-west and you'll see the bald guy you need to kill with two other enemies, look towards the admin building tower and you'll see the black guy with sunglasses you need to kill. Kill the bald guy first then the black guy quickly, call the heli back to where you started and try to get get out of there without being seen.

Thanks to PowerPyx for this strat, his video will make it much more clear, I didn't do a good job at explaining this one.

This one isn't too hard, you just can't kill a single person so stick with the stun revolver. The AA gun later in the mission shouldn't shoot you down so don't worry too much about that. The APC you have to destroy doesn't count as a kill so go ahead and destroy that with a recoiless rifle. You can take out the chopper side gunner with the stun revolver as well.
This will also get you the "Pacifist" achievement. (You can use the way I explained on the hard, since its much easier, but you wont get the achievement.)
Ride the truck until you get into the admin building, go up the admin building watch tower and grab the tape, shoot the camera with your silenced rifle first though, pick up the tape and go back into the truck and wait until the driver gets back into the truck and drives out the map. This will also get you the "Infiltration" achievement.
Also make sure you don't tranq the driver, restarting from the last checkpoint de-spawns the truck so you'll want to avoid getting caught.
This one is a little bit more trickier since you don't start with a silenced weapon. Ride the truck until you get into the little tunnel and jump out. Ahead of you will be an APC, get into that and start driving towards the main gate. The door next to the gate will be the one you'll want to go through. Just remember you have to park the APC so the front is facing the way you came or else you'll get out the wrong way and you'll be detected. Go into the boiler room, hold up the guard and get the tape from him. Get back into the APC and drive out the map. Keep in mind crashing into something will alert the guards.
This can also be used for normal but you won't get the "Infiltration" achievement.

For this you'll want to be as fast as you can. This is much easier if you have gotten an A rank and unlocked the recoilless rifle, but if you haven't don't worry it's still possible obviously just not as easy. You'll want to avoid killing anyone, getting an alert is okay and hell, chances are you will be getting detected. From where you start you're going to want to plant a C4 on the AA gun you can see from the starting area, make sure there aren't any guards around the AA guns when they go off. Go towards the helipad and there will be another two AA guns with explosive barrels next to them at the end of each side. Shoot them and detonate the C4 you planted earlier, doesn't matter what order you do it in. Now the APC will come and you're going to want to destroy that as fast as possible, use grenades, lure it into the claymores near the prison camp, steal a recoilless rifle from an enemy or an armoury, whatever would be the quickest I guess.
The same could be applied to hard but I'm not totally sure, I haven't had good luck with this mission.
So you've tried this mission in the past and gotten at least an A, well lucky you this mission will be a breeze. As soon as you start call the helicopter to the cliff where you start off in the main "GZ" mission, pick up the recoilless rifle and blow up the two AA guns you can see in the distance near the helipad. Destroy the AA gun closest to you, wait for the APC to come down the road in the distance, destroy that, get into the helicopter and you're done. 2ez

This is the easily the easiest mission to S rank since there's not many guards. Re-create at least 3 - 4 scenes and head for the exit. The main key to getting an S rank is your time, so complete it as fast as you can. All though you need to complete every scene in order to trigger the quiz.
This is not too bad at first but the last part can be tricky. You can only kill the snatchers, not the normal guards so make sure you tranq them instead. Also I don't think you can have any retries. Tranq / kill the enemies through the refugee camp and warehouse area until you get to the helipad, head across to where the door is next to the main gate and and tranq the guard around there. Go inside, shoot the cam and go down the stairs the kill the other snatcher, there's another guard next to Paz's cell so kill him as well. Go outside the boiler room into the middle, there will be three guards, 2 snatchers 1 normal, try and wait until the normal walks away and tranq him, quickly shoot the cam out and kill the other 2 snatchers. Go into the armoury and grab the recoilless rifle and the silenced rifle. Go back out in front of the main gate and tranq / kill the other two guards in the car. Wait for them to stop, tranq the real guard and kill the other. Remember the real guard will always be in left seat.

Now this is the hard part, wait for the helicopter to arrive then quickly shoot the guard in the watch tower. Quickly run towards sorta near the drainage tunnel where the XOF patch was and go prone, shoot the snatchers you see come running out the main gate. There will be more coming out the side door next to it so throw some grenades around it. Quickly run towards the AA gun towards where the two other snatchers come and kill them while prone. Take our your recoilless rifle and shoot the helicopter that comes. Start aiming the recoilless rifle at the door in the admin building. When the bunch of snatchers run out the door, fire. If done correctly that bunch should be dead, shoot again when the second wave comes out. Make sure you save at least 2 or 3 rockets for the helicopter. Shoot down the helicopter and get out of there.
You will also get the "Hidden" achievement if done right.

So in short you want to avoid getting an alert, a single one will screw it all up and you'll have to restart

I probably could of somehow made that much shorter.

In order to trigger the quiz you need to re-create every scene, doesn't matter what rank so feel free to go loud. (All though you could miss out on a scene or two if you kill the wrong guard) Normal and hard will have two different quiz's. 10 questions per quiz.
Re-creating every scene will also get you the "Reminiscence" achievement.

QMGS1 featured Solid Snake infiltrating which island?

AShadow Moses

QThe remote-controlled missile is known by which nickname?

ANikita

Q.Who did you need to call on the Codec in order to save your progress?
A.Mei Ling

QThe Next-Generation Special Forces who took part in the uprising with FOXHOUND were given what treatment?

AGene Therapy

QOn which floor of the Nuclear Warhead Storage Building was Otacon's lab located?

A2nd Floor Basement

QWhat was the Cyborg Ninja's True Identity?

AFrank Jeager

QBefore being called back into action for the mission, Snake lived in Alaska as a...?

AMusher

QWhat was the maximum load of the elevator in Communications Tower B?

A650 lbs (300 kilograms)

QWhat type of storage media did the ArmsTech president give Snake?

AOptical Disk

QWhat is the title of the ending theme?

AThe Best Is Yet To Come

QWhat did Snake call Otacon's love for a certain female character?

AStockholm Syndrome

QWhen Otacon visited Snake at his cell after he was captured, he gave him what level of security card?

ALevel 6

QWhich boss character was NOT a member of FOXHOUND?

ACyborg Ninja

Q.What was the name of the studio (later renamed Kojima Productions) that developed MGS1?

AKCE (Konami Computer Entertainment) Japan

QWho did Otacon fall in love with in MGS1?

ASniper Wolf

QHow did they censor Johnny Sasaki's privates in the U.S. release of MGS1?

APixelization

QSnake attempted to give Meryl a handgun of what caliber?

A.45

QAfter escaping the base, Snake and Meryl encounter a family of which type of animal?

ACaribou

QIn total, how many prototypes of the stealth camouflage did Otacon build?

A5

QWhat did the "P.A.L." in "P.A.L. Key" stand for?

APermissive Action Link

Completing the normal quiz will get you the classic PS1 Solid Snake skin, completing the hard quiz will get you the Frank Jeager skin / classic snake with Frank Jeagers exo-skeleton

I'm not totally sure if this counts towards 100%, but if you still don't have it this would be worth a try.

By now you should of extracted pretty much every POW, they will always be at these locations

-Old prison area
-Paz's cell

You will also need to extract the two targets from the "Eliminate the Renegade Threat" mission, doesn't matter what rank. How you extract them is up to you, just remember to tranq / knock them out.

So you've

-Gotten all XOF patches
-Gotten all cassette tapes
-Unlocked every trial
-S ranked every mission
-Extracted every POW

If I forgot to list anything you might have achievements left over, so go ahead and get them. By now you should have 100%

so

(btw eva is a really good anime everyone should watch unless you're a pleb)

"B-b-but w-will I even get anything in TPP for getting 100%"

I'm not totally sure, but I do know for sure that if you own GZ you'll be able to recruit any POW's you recovered as staff for the new Motherbase, and maybe even the undercover and bald soldiers in the Classified Intel Acquisition mission (since when you mark them they glow like Glaz & Politz. And if you extracted them too obviously) I think you might even get the GZ sneaking suit, of course these don't require 100%.

Edit: Turns out you'll get all those rewards even without 100%, so at the moment it's just for bragging rights really.

Thanks for reading this, this is my first guide. Sorry for all the grammar mistakes, I'll get around to fixing them sometime.