At my local GameStop. I'm tempted to go, they're going to use Pokemon Battle Revolution and the Battle Tower level 50 rule thing, whatever it was (where Pokemon over 50 get lowered to 50 and under 50 get raised to 50). I, however, have this terrible feeling some 10-year-old is going to destroy me.
Here's my three of my team for the time being, move-sets and all. I don't really know if there's much I could do to improve them by tomorrow though.
Charizard (Coltrane), level 66;
@Flame Plate
Wing Attack, Flamethrower, Flare Blitz, Flamethrower
Leafeon (Elliot), level 65;
@Miracle Seed
GrassWhistle, Razor Leaf, Last Resort, Giga Drain
Weezing, level 55;
@Quick Claw
Double Hit, Explosion, Sludge Bomb, Destiny Bond
Weezing is obviously going to be an all-or-nothing Poke, going in with Explosion or Destiny Bond (he was 55 when I caught him). Charizard and Leafeon I've raised from level 1, so I like them a lot, but I'm really thinking I need to replace Flamethrower and Giga Drain.
Pokemon I have in boxes that I've been considering raising (via EXP Share) for tomorrow:
Gengar (Jerusalem) level 31; Raichu, level 44; Eevee, level 5; Mudkip (MUDKIP), level 15; Riolu, level 31; Gardevoir, level 33.
Any suggestions would help greatly.
Definitely run the Gengar, so you have something to switch in against a physical attack. You should also use your Riolu, evolve it, and give it Endure/Reversal and sweep everyone (try to get a Salac Berry if you can, and give it to him). Use Gardevoir as well and pack it with a bunch of special moves and Will-O-Wisp. It's short notice, but if you can give your other pokemon some decent movesets, you may be able to take a decent place.
http://www.smogon.com/forums/showthread.php?t=20686
edit: some general advice; know your types (fire, water, etc) well, so you know what to switch in when another pokemon is in trouble. That's probably one of the single most important things that you need to know. Also, know your stats. If something is high in Defense, you're safe to switch it in against a physical sweeper (as long as it doesn't hit you for a super effective). etc.
good luck