>>59733386You need to know the right people at the right time. If you somehow manage to meet one of them, there's 99% chances that she's already taken.
If she isn't: then you only have one single chance with her, if you fuck up once it's Game Over. Also, those kind of girls always have a ridiculous amount of guys orbiting them, especially in the anime/cosplay community which means you'll have a lot of competition.
tl;dr:
You don't.