There are only two instances where anyone should feel like an outcast and at a con isnt one of them. Everybody is there to have fun, eat bad con food, and hang out with people that are into the same weird stuff they are. Last con I went to I ended up; playing D&D, dancing with the hotel manager, sneaking my way into one of the luxury suits by pretending to be one of the bellhops, and leading the effort to get the con's band to play "Come Sail Away" getting nearly half the con to burst into song in the process. Con's are nothing but good fun, good friends, and legally questionable good times.
Maybe I just go to a good con but I've always felt perfectly at ease around the people there. I don't cosplay, I can count the number of anime I've watched on one hand, but I've never had a problem getting along with even the most hardcore anime enthusiasts (I actually had a pretty good conversation with a guy dressed up as a mudkip). That being said I will advise you avoid crossdressing cosplayers of your own gender they are very...exciteable...don't ask.
The only advice I can offer for being at a con is let loose, never hold back, don't think before you act or speak, and talk to everyone you meet...and keep a mental map of all of the elevators and stairwells
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