How can I be more friendly?

People tend to think I'm a b**** because I unfortunately don't have censor when it comes to saying what comes to my mind. If I have an opinion on something, people know about it. I have a very dry sense of humour so people never know if I'm joking or not (I'm usually joking). I don't want to change who I am, or be nice to people I think are f**** heads, just maybe not be so brutally honest with friends. I don't like hurting friends feelings but I don't know where to draw a line, mostly due to the fact I'm a bit of a robot.