i second (er...third) the vaseline idea. i had braces before and just from having braces plus the appointments of them opening up my mouth and stretching my lips farther than it should...it really works!

plus extra tip, if your lips are dry (especially in winter) and you want to exfoliate them don't use normal skin exfoliator since the skin on your lips are much thinner. instead, wet your lips with water and use sugar to exfoliate, just keep rubbing it till it melts away.