To get into character...
Gypsy - Watch the Princess Bride the night before an event, listen to some belly dancing music, stock up on sugar, splurge and buy a new skirt or jingly dance belt.
MWE - I have two mixed CD's specifically designed with music that makes me think of her. Watch Braveheart, Rob Roy, Labrynth, Legend, Dark City (just 'cause), First Knight, Dragonheart.
Dark Elf - Listen to Industrial/German Hate rock, let my mind think of all the evil things I normally suppress.
True "How To" always comes once I put on the costume and makeup though.