Let's see, how to answer this...
I almost always play males. Not that I have any particular aversion to playing a female, just no real desire to. Physically, I tend to model alot of my characters after my real self (at least lately, it wasn't always this way). I also have quite a few character that resemble me in personality too. I think the reason I gravitate toward this is because it is far easier to act like yourself than someone else. The bigger reason is that, by acting like myself and reading back over it later, I am able to discover some flaws of mine and subsequently work on fixing them. If I read over my post and realize I sound really cocky, or annoying, or whatever, then I am able to find out things about myself. Of course, I haven't always done this. I've played a few characters that were more introverted and quiet (which is so not me in real life).
Also, all of my characters to this point have been on the good side (if I remember correctly, I've made a -lot- of characters). Although, I'm intending to play a bad guy in an RPG I'm writing soon. Most of my characters tend to be the chivalrous type, protective of their friends and with well-developed senses of justice. This is a theme I use frequently when creating my characters.
I dunno what else to say. Anyone else have any insight into my characters?