10* things I wish I knew sooner...

The advice is still valid through the Oil Update.

1. Food Management - If you set your Rations Box to Priority 6, when you dig up food while exploring, your Dupes will automatically bring it to the box. This also applies to food that has been harvested, and cooked.
   
2. CO2 is Sterile - Food does not rot in a sterile environment. If you place your Rations Box fully submerged in CO2, the food inside of it will not rot.
   
3. CO2 is heavier than O2 - Assuming you have O2 generation in your base, CO2 will sink downward. Create pits toward the bottom of your base for food/CO2 storage.
   
4. Food/Item Transfers - If you set your new Rations Box/Storage Container to Priority 6, and a different one has a lower Priority, your Dupes will automatically transfer the items in them.
   
5. Don't kill Hatch's - Seriously, don't kill them. This one was embarrassing as hell. I had no clue that they make coal. Coal is used for power generation a few cycles in via Coal Generator. If you build a storage compartment near them, and fill it with dirt; you can feed them to keep making you coal. If you have all tile underneath them, the Hatch's never go to sleep.

   Just turn off combat. It's not needed right now unless you run into Morbs.
   

6. Base Design - Base design is important. You need enough space in each room for items, and decor, while enough space between rooms to allow for airflow (thus needing less O2 producing items.) Creating a 3 block space between rooms. Room 1 ends, empty tile, ladder, empty tile, room 2. Dupes can jump one space, land on the ladder, and go to the next room. Having a 3 open block space between rooms provides better air flow for Oxygen. - Refer to the Image section below.
   Update: With the Oil Update, massive open space designs are still valid, but are lower in popularity due to the bonus' inherent in room designations.
   
7. Room Designations - If you select the new overlay, there are instructions on how big to create certain rooms, and what facilties are required. By meeting these requirements, your duplicants receive a bonus, or reduction to stress while occupying these rooms for their intended use.
   
8. Algae is Limited Early Game Early game - Algae is limited. Move on to Electrolyzers for O2 until you can SAFETLY enter the Slime biome.
   
9. Food Priorities - So my Dupes would always eat Meallice, and I could never make bars. I had no clue that you can set your Dupes to not eat certain foods. Color me stupid.
   
10. Population Control - You can reject taking on new Duplicants. You should NOT take more than 6-8 until your colony is fully stablized.
    
11. Building Rotation - Certain buildings can be rotated using the O key.
    
12. Such as airlocks! - Airlocks can be rotated to be up-down rather than left-right!
    
13. Airlock Control - You can prevent certain Dupes from using an airlock by clicking it, and choosing access permission.
    
14. Abyssalite - Abyssalite Is great for keeping a cold area cold, or warm area warm, BUT if you take Abyssalite from a warm area, and try to tile a cold area, that Abyssalite will maintain the heat from the area you harvested it.
    
15. Slime Biome - Do not rush into the Slime Biome. Slimelung can seriously mess you up if you're not careful. Make sure you've multiple airlocks, wash basins, and ore scrubber setup before entering one. Limit how many of your Dupes enter at a time.
    
16. Who do I start with? - 1 dupe with Learning, 1 dupe with Cooking, 1 dupe with Creativity. You can't guarentee what you're going to get, but the three I've listed are your main priorities. You'll want to max out your research ASAP, and you'll want someone who can make quality art ASAP. The cooking is a bonus.
    
17. Priority 9 - If everything is Priority 9, then nothing is a Priority. Use the Priority system appropriately. Set the numbers in the order of importance. These priorities counts for delivery of goods for cooking, science, and O2 production as well.
    
18. New Dupes - Thank you to @Pablow ♥♥♥♥♥♥♥♥, if you save before selecting the portal when new Dupes arrive, you can simply reload if you're unhappy with the selection provided.
    
19. Pipes/Wires - I always knew this one, but it surprises me how many folks never realize while playing. You can hide wires/pipes behind tiles, and will not take a decor penalty for doing so.
    
20. Courtesy of Baelorack - Power Consumption - Be carefuly how much power consumption you put on wires - 1000w max consumption (F2 to check). This is how you avoid wire damage.
    
21. Courtesy of Baelorack - Power Transformers - Make sure you connect your power producers to the big side and receivers to the small side of a transformer.