also.
(haha. sorry. This girl just won't shut up will she???)
In terms of how I pick? because I am so obsessive with sewing, I try to keep a list of projects I wanna do, including costumes. I have a excel page where I keep track of every character from all the things I love that might someday wanna do. I also have all the girls from my cosplay group, so well all share ideas and what we wanna see eachother do, as well as do ourselves. We also have a "joe nobody" column where we put costumes that we wanna see or make, but nobody in our group right now could pull off.
That way, when the time comes to pick costumes for cons, we just go through the list and see what we feel like doing. It's also really nice, if you go with a group, to co-ordinate, so that you have a troupe to pose with, and hang around with.
They don't even really have to be from the same thing.
Like...this year. One of our group wanted to do a horde of moogles. So we all agreed, except for one, who had already picked her three days of costumes. So she comrpomised.
She was gonna do Beast boy from teen titans, who has the power to change into different animals. So now she's doing beast boy, with a green moogle ball. It's a stupid joke, but it makes us laugh, and that way we all re-inforce each-other's excitement for the con.
Cheers!