To me the biggest turn off is if it's obvious your trying to hard and acting like your el suave.
Or being dishonest about yourself at all as it's obvious to tell when guys are acting one way to get in your pants, you can still see through that, your gonna slip somewhere and we'll see your one of those jerks that probably talks about how he's gonna hit that to his friends. And unless your a girl who doesn't care and just wants the same thing then your in luck.
I have to say also, talking about women like were nothing more then a piece of ass isn't going to get you there either.