its not that girls like assholes. ok well some do but personally i think they're weird. it's that those guys appear to us as strong, masculine, confident, outgoing and know what they want. those are very attractive characteristics so girls tend to gravitate towards guys like that. as far as bad boys go, girls love to have a wild good time and those boys help us bring that side of ourselves out. i <3 my bad boy.
what i'm saying is, be a gentleman. i remember one guy opened the car door for me once and i was shocked. there are so few guys that still have those gentlemanly manners and that's too bad
so be assertive and try and be confident but not an outright dickhead to her.