Agree entirely with Firex ;P Don't buy women drinks it's potentially the neediest thing you can do, also chatted to enough women to know that they actually look down on guys who offer them drinks. It immediately devalues you.
One girl I got talking to the other night was a bit of a tomboy

Wasn't really interested but she was really fun to hang out with, she actually tasked herself with pissing off guys and still managing to get drinks out of them. She immediately did this by throwing her empty cup at the back of a guys head, he winked back so she did it again... This actually ended up with him coming over and offering to buy her a drink >< I was amazed to be honest and a little freaked out by this revelation.
In short, no don't ever do it. No woman will respect you more for it until after you've slept with them *amusingly*