After an interview, some job seekers write THANK YOU LETTERS...some don't. Don't miss the opportunity to set yourself apart from the other job seekers. At the very least, a thank you note will remind them of your interview, confirm your interest, and associate warm fuzzy's with your name. You may even tuck a nugget into the letter that you may not have mentioned or want to highlight again...ALWAYS send a thank you letter!
If you get nervous and tend to overcompensate by presenting as overconfident or arrogant, you might try the following to see if it helps.
After an interview:
Apply this same approach after an interview with any other aspects of interviewing you find you need to address: Nervousness, fidgeting, head-bobbing, etc.
Everyone hates to hear it because they say they feel stupid or silly, but you must PRACTICE. First in the mirror then with a friend then with a respected instructor or other "superior." The more you interview, practice or otherwise, the more comfortable and confident you will be when it really counts. Practice, practice, practice!