Train as much as you can before so you are prepared for anything.
Focus on a skill to practice during training.
Get sponsors before the games and be as likable as possible. Find people who will give you help in the games whenever you need it. Image courtesy of College Humor.
Pretend to be mediocre during training to make people forget you.
For the first days in the arena, make your main goal to hide and gather weapons.
Be careful what you eat - make sure your food isn't posionous like the berries above.
Set your camp out of people's sight - place resources up high in a tree so people won't see them easily.
Have plenty of food and water available.
Stay away from fire, tracker jackers, and any obstacles thrown at you.
Once the number of tributes goes down to lower numbers, use the element of surprise to eliminate the rest.