Anyone here ever studied it?
Ever think about the way the people you know behave in different situations?
Gives you quite an insight to their thinking.

Body language is so important...wayyy more important than verbal communication.. if you know the signals you can respond accordingly..

Unsmiling and Crossed arms can mean a lot but usually say - stay away..I'm not open or receptive to what you are saying. I'm defensive and closed minded. (My suggestion - run like hell.)

Mirroring - if someone is unconsciously mirroring your moves, then they might be more willing to hear what you are saying and are interested in you.

Scanning the room, no eye contact = I'm more interested in the other side of the room.. I'm not into you

Darting eyes, can't look you in the eye - uncomfortable, may be untrustworthy - possibly lying like a dog

Smiling, wide gestures, touching your arm, hugging - go for it.

Unsmiling and Crossed Arms - could mean "he/she acts so needy and stupid that if I make any type of friendly gesture, I'll never get rid of him/her, with a little work, maybe he/she will run like hell"

Mirroring - they may be trying to determine if your moves are of a sexually confused nature or you may actually be saying something interesting.

Scanning the Room, no eye contact - may be nervous around you, he/she may feel they could melt if they look into your eyes.

Darting eyes, can't look you in the eye - for god's sakes, stop staring at him/her and they may feel comfortable enough to look at you, again, they could just be really nervous around you.

Smiling, wide gestures, touching your arm, hugging - married!