When you first walk into the interviewer's office, make a conscious effort not to rush things. Pause at the door to make sure that the interviewer is ready for you before you walk in. Take a few seconds to look around and acclimate yourself when you enter the office. After you and the interviewer greet one another and shake hands, take your time when settling yourself into the chair. By taking things a little slower, you appear more poised and professional. Just bear in mind that this tactic doesn't work if you do it in a forced, unnatural way.