How To Win Diplomacy On Any Difficulty

Start Your Game and Choose to have Diplomacy as your win condition.

Before casting your vote, quicksave.

Almost EVERYTIME the AI will always choose the same results when it's time to start voting.

Memorize the choices. Submit your choices. Memorize the end result.

Reload.

Choose those choices after you reload.

If you get voted to loose diplomacy, choose that option and it will offset.

Rinse, Repeat, Reap the Reward.