Eye Contact: Always maintain eye contact with your audience. However, a person must ensure that he / she should not fix his gaze at one person for more than 5 seconds. Too much fluttering of eyes could indicate lack of confidence. Staring at a person could be daunting and hence is not such a good idea.
Hand Shake: While shaking hands especially in a professional environment, the hand shake should be firm and not loose. An iron handshake [very strong handshake] can indicate that a person is trying to dominate.
Crossing your Arms: Crossing your arms could imply that a person is not open to new ideas / opinion especially in case of giving a presentation. However, in a one-on-one interview if the interviewer has his / her arms crossed, the candidate could do the same.
Sitting Posture: Leaning on a chair is not a good idea. One must sit upright though in a relaxed position. Sitting back in your chair implies lack of interest or rejection.
Gesture: Gesture refers to a type of non verbal communication which uses a part of the body with or without verbal communication. Gestures include facial expressions, nods [which is a sign of approval in most cultures], head bobbling / shaking.
Facial Expression: The face is a best reflection of what a person feels. More often than not it is easy to recognize if a person is happy, sad, anxious, irritated, or excited. It is very important that in a professional scenario a person must control his / her facial expressions. For e.g. If a presenter gets a feel that his presentation is not going on very well, he / she should not show the sign of losing of hope and instead try for a greater involvement from the participants.