But there are ways to reduce your chances of being rebuffed. There are a few different ways to tell if a woman is approachable in a bar, club, or other social gathering. First, pay attention to how she interacts with her friends. Actually, first, find a woman. Then pay attention to how she interacts with the people around her.
Women are different.
Sometimes they don't want to be approached. Go say hi. Personally, I would stay away, since I know next to nothing about the subject. But if you happen to have, say, a PhD in organic chem, you might want to offer your help. And offer to buy her another coffee, unless he hair is already standing on end.