I'll answer any questions. Usually I talk to girls in close, but not too close manner.
When you talk to girls, the spotlight should be on them, what their interests are, what they think, what they feel.
Don't bother talking to girls about crap like, how did you do on your test, or how do you think the weather is.
All conversations should be based on opinions and feelings. That's huge, and you should listen and respond to what they say.
When I see girls I know, I usually give them a hug, (out at parties and stuff, not when I just randomly walk by them).
If I see girls that I know, then I give them a smile and a hi, (I usually don't feel like talking to girls that I don't really know unless I'm drunk).
Just let them know they are known and that you remember who they are.
Many guys over-do things. They think that they have to get to know girls really well, and have to talk to them on the phone and stuff just to spark an interest.
Girls can be easily influenced with a hug, a smile, and a few conversations during a party that interests them.
I have more, just ask.