I saw this:
http://www.mmowned.com/forums/world-...g-bracket.html but it didn't seem to explain how to do it correctly.
What you do (assuming you want to lvl 60 twink) is to not upgrade your account to BC. Turn EXP gains off, and turn on the Blood Crusade trial found in account management. Do some level 60 dungeons in Blood Crusade, and get friends to run you/do quests for badass gear. Now put the Blood Crusade enchants (and gems) on your gear. Basically as everyone knows Level 60 BC gear > Level 60 Vanilla gear. Plus, you get enchants, and gems which aren't even available in Vanilla.
Now, when your trial is done, turn exp gains back on. You won't gain any levels since Vanilla accounts are unable to get past level 60. You can twink at the top of your Alterac Valley bracket with the normal toons, and roll face. Have fun.
(Note: can also be done with WOTLK)