In terms of gameplay:
Do not practice anything new 1-2 days before the tournament.
Work on whatever you already know, and practice on getting it perfect. If you try to incorporate something new right before a tournament, it will distract you during the match.
Practice Tech Skill
No matter what game you're playing, there is always a technical aspect to it. The worst thing to happen in a tournament match is when you lose because of an SD, or because you flubbed a wavedash/L cancel/b-reverse.
In terms of personal things:
Go the **** to sleep.
A lot of players tend to practice the entire night before, and go to the tournament tired. From my experience, this is detrimental to your performance. Practice, then sleep. If you wake up early, play for an hour or two before you head out to the venue.
Eat breakfast.
There is no guarantee that you will have a lunch break at big events, and there is no guarantee you'll even WANT a lunch break with all of the new players around. Make sure to have a filling breakfast, so you can go as long as possible without food; that way you can get more friendlies in~
Bring water.
I have made it a habit to buy a gallon/2 liter jug of water before a tournament, and carry it with me all day. Staying hydrated helps you in so many ways there's no point in even listing them.
Have fun.
Sounds stupid right? It isn't. Your goal should NOT be to win the tournament, unless you already know you have a real shot at it. Play as many people as you can, get as much experience as possible. This is how you improve the fastest. If you are not having fun while you do this, you might as well quit. Remember, it's still just a game, the point of playing is to have fun.
