my boyfriend saw this french maid costume that he thinks would be really hot... I've just never done anything like this before. So how would I go about wearing it, and presenting myself in it in a sexy way?
Since he is your boyfriend, he must already find you sexy and I think if you present yourself as a French speaker who doesn't speak any French and just remain silent in it then you couldn't go far wrong. Maybe teach yourself a couple of sentences in French like "I don't understand" just to add a bit of realism. Just "Oui" and "Non" should serve you well though. Generally though remaining in the shy, quiet and I suppose 'naughty' maid persona should serve you well. Good luck!
Buy an extravagant feather duster- not a boring domestic-looking one, but something completely frou-frou (you can get big ostrich feather ones that are glorious). Put on the costume, and get him to lie on the bed. Parade around the room, pretending to dust but really showing off your body, bending over artfully, and stretching yourself. It helps if you have some louche music on to move to. Slowly - very slowly - move closer and closer to him. Talk to him all the while as if you're a maid anxious to do a good job. Tell him what a handsome, attractive 'employer' he is and how much you like 'working' for him.
Once you're close, look up at him innocently and ask him if there's anywhere he'd else he'd like cleaned, while brushing your duster against his body. Then take a single feather and tease him with it.
I'm sure he'll be more than ready to take it from there! :)