Thank the interviewer(s) in person, by email or by post. Common courtesy and politeness goes far in interviewing.
Don't brag too much. Humility is persuasive.
Remember the importance of body language such as eye contact, posture, active listening and nodding.
Be authentic, cheery, attentive, confident, frank and succint.
Dress for success. Dress stylish and precise.
Do not be late. Prepare for the unexpected.
Research the market, interviewer, and job opportunity.
Job Hunting Tips:
"Before you have the interview find about the employer. Get to know what the firm does, who their competitors are, and their principles. An interviewer will not listen to what you say if you don't understand how they do things."