It also depends on if she likes you. Its a great indicator either way. Pay attention to how she responds. If she pulls away orgives any impression that she feels uncomfortable being touched by you, then take it as a pretty clear sign that she isn't really interested.
On the other hand, if you can comfortably place your hand on a girl's shoulder and she obviously doesn't mind, then it is again a clear indication that physical contact is accepted. If that's the case, then step it up.
I'm a very physical person. I'm always hugging and touching my friends (guys and girls) because humans do like physical contact (if they like you). It strengthens bonds and increases rapport. It also makes it much easier to touch a girl when I meet her because I am naturally that way.
If you are talking to a girl at a bar/club and you have a hand on her shoulder (and she obviously doesn't mind) step it up a little. I like to place a hand on her waist or hips while I talk into her ear. If you're smooth you can set up quite an embrace from one little conversation.
Another thing I like to do when I first meet a chick is to shake hands on introductions, but don't let go. Don't grip tight and make her feel trapped, the trick is to have a light grip that she can pull away from at any time but SHE will be the one to break contact no matter how long it takes. The longer it takes the more clearly she is into you. Sometimes you can chat away for ages and you both kind of 'forget' you're holding hands, as if it is the most natural thing in the world. And it's a definite green light for more kino.
