Girl help?

ok i have a problem. i tend to do/say really dumb things around females or so im uming because im not very successful with women. im not a very bad looking guy either(or atleast people have said), and friends have told me and confirmed with me countless times when specific girls do like me. i have no idea what i am doing wrong. can someone please just llend me some tidbits of info on adapting when hanging out with girls and not saying/doing dumb things when with these girls? sorry if this is confusing... i feel like im kind of rambling