Mirror - One sign of compatibility is the unconscious act of mirroring someone's movements and mannerisms. Watch what your date or someone you are interested in is doing and follow suit. Smile when he smiles, laugh when he laughs etc. This can create a sense of similarity and closeness in a short period of time.
Slow everything down - Actions like walking too quickly or waving wildly from across the room can make you seem manic or stressed. Slow everything down to show that you are relaxed and confident. Don't snap your neck to look at someone when they address you, don't run across the room when you see someone you want to talk to etc.{relatedarticles}
Arms - You've probably heard this one before, but standing with your arms crossed sends a signal that you are being defensive or closed off. Standing with your arms straight stiff to the side also sends a bad message of anger or anxiety. Instead, stand with your arms relaxed at your sides, and if you are sitting, keep your arms folded casually in your lap to show that you are approachable and not hiding anything.
Legs - When standing, the position of the legs is a good indicator of your confidence and mood at the moment. Standing with your legs shoulder width apart demonstrates to those around you that you are relaxed. Taking an even wider stance shows control and that you are grounded. Sitting with your legs uncrossed, much like arms, shows that you are not in "protective mode" and are open to interaction.