Nothing is as awkward as offering your hand and having the gesture not returned by the other person. Therefore you should wait for the interviewer to offer his or her hand first, but be ready to offer your hand immediately. Some experts suggest talking at the same rate and tone as the interviewer. For example, if the interviewer is speaking softly, so should you. They say that body language gives more away about us than speech.
Eye contact is very important but make sure it looks natural.
A smiling, relaxed face is very inviting. Hands resting casually in your lap rather than arms folded across your chest also is more inviting. If you normally move your hands around a lot when you speak, tone it down some. You don't want to look too stiff, but you don't want to look like you are a bundle of nervous energy. Speak slowly and clearly.