How to tell a girl that you want only to stay as friends?

Some girls don't care about that and would be able to talk with me. Unless I bring up conversations about sexual organs or sex, then they might be a bit freaked-out. But I'm not a freak, I just want some space.

Just be like, yea yesterday i got Hammered and today woke up... took a piss... shaved that gotee... kicked the girl out

Thats how my bro talks sooo yea.