Crossing your legs at the thigh is considered a feminine mannerism? I always thought of that as a guy thing-- not even kidding. Not that that makes much of a difference in my case, since it's not a very comfortable position for me. I usually sit cross-legged ("Indian style") or kneeling in public, and when I'm alone/with friends, I often curl up in my chair with my knees at chest-level (or alternately, curl one leg up "Indian style" and pull the other one up to my chest). I sit funny... not really masculinely or femininely, I guess. Just weirdly. x3
In any case, I don't really try to "fix" my mannerisms, usually. I know I have a ton of "feminine" mannerisms, but they don't bother me. For one thing, I've met plenty of guys (many of them not even gay) with similar mannerisms. For another thing, my mannerisms are a part of me. It would kind of defeat the purpose for me to sacrifice perfectly fine, even good, parts of myself just to pass better. Sure, I talk with my hands and wear my enthusiasm and affection on my sleeve... but if i didn't do that, I wouldn't feel like me.
One of the few mannerisms I do kind of try to avoid, though, is swinging my hips when I walk. I've never really lived that I do that... it's just that that's kind of what automatically happens due to how my body is set up, so it happens by default unless I conciously avoid it. x3;