Body language is composition of posture, gestures, facial expressions, voice etc. You can control your movements by following simple guidelines mentioned below:
Interviewers know that you may be nervous, but if you are feeling really nervous, you could concentrate on controlling your breathing. The way in which you breathe affects the rhythm and pace of your speech. If you take short,sharp breaths in upper chest, you force yourself to breathe too often to sustain your voice. Unnatural pauses and gasps will punctuate your speech. You should pause at natural breaks to take in your breath. Pausing in these natural breaks provides a further benefit - it gives you some time to think about what you want to say and hence control the content of your speech.
If you do not know what to do with your hands, clasp them or put them on your lap. Avoid small repetitive movements: if you keep moving your feet, smoothing your hair or nibbling your fingernails, it will distract the interviewer and indicate that you are nervous. Avoid any side to side swaying movements.
Make sure your body language is sufficiently receptive. Don't turn away from the interviewer, or wrap your arms around your chest in self-protection. Don't gaze out of the window as that gives the impression that you are not interested in the interview process. Always try to look the interviewer in the eye while answering questions.