I've met a few girls, usually friends of friends, who seem to give mixed signals to the point that I actually pass on other girls, parties etc., to spend time with them.

This kind of girl seems into you half the time but when you get closer she backs off. If you have something else to be doing she'll beg you to stay and hang out with her but if you start giving her attention she wont give you any easy signals. You scoot up next to her and she makes an excuse to move somewhere else. But another time, say in a bar, she'll have her arms around you, full on, making all sorts of excuses to be close to you, for example to take loads of pics of you two.

How do you deal with this, how do you spot it and how has this kind of girl worked out for you?

I don't think I need to mention that they are always gorgeous enough to catch your attention else you wouldn't give a fuck. When you go out together with friends she could have any guy in the club but she seems equally disinterested.