Firm hand shake.
Keep eye contact.
No coins or keys in your pocket to reduce rattling distractions.
Keep hands outta pockets.
Go in there with the confidence that you deserve this job. (Not cocky though)
3 copies of your resume on hand
Bring a note pad with questions to ask the interviewer.
Smile.
Just relax and keep in mind they put on their pants one leg at a time too.
Best of luck buddy.