How do you act when you cosplay?

Depends on the event, and I do usually crossplay, so I try to behave as "male" as possible (it's hard to remember to always walk like a guy while in costume!). If I'm at a con and stopped for a photo I'll definitely strike the correct pose. If I'm appearing in something like a parade, I will do my best to stay in character the entire day. However, if anyone speaks to me at a con or elsewhere, I totally drop the character routine (unless the other person wants to act out a little scene or something). I never get into costume or remove it in view of the public. I prefer to maintain the illusion that the character everyone is seeing is "real". You know, like in the Wizard of Oz..."Don't look behind the curtain!"

The definition of cosplay is literally "costume play," so I feel playing the part (on whatever level makes you comfortable) is integral...otherwise you're just walking around in a costume.