adman -
You have to use the Versus Seeker that was giving to you by Dawn/Male Counterpart. It takes like 100 steps to recharge though, and sometimes they don't accept it. BUT, if they do accept to battle you after using the Versus Seeker, there will be an "!" above their heads; afterwards, you just have to talk to them to activate the battle.
If you want them to level up their pokemon, I think you have to beat the game first (I always thought that they were leveled up just by using the Versus Seeker).
Use an Amulet Coin also if you want more money.
squeaky -
I think berries and such disappear during normal gameplay after being activated, though I'm not sure. I know for a fact that no item disappears permanently if it is used in a Wi Fi battle, or in a battle against friends or battle tower. Focus Sash and such never disappear even after activating in a normal battle though.
Too_Hungry -
http://www.smogon.com/forums/showthread.php?t=17887
This thread might help you.