Do's:

• Research the company
• Prepare small talk topics or look for items in the interviewers office to ask about on a personal level
• Prepare the night before. Think of questions you may be asked and rehearse in a mirror
• Be early - 5 minutes is fine but not more than 10 minutes, you don't want the interviewer to feel pressured to start the interview early
• Bring multiple clean copies of your resume and references 
• Dress professionally
• Give them every reason to hire you
• Smile
• Greet the interviewer with a handshake
• Stand up straight
• Mimic the position the interviewer takes
• Laugh if a joke is funny
• Accept water if offered
• Prepare questions:
  • What a "day in the life" is like?
  • What are they looking for in an employee?
  • Why would you want to work there?
  • What do employees like best about working there?
• Ask about what to expect next
• Ask about what the next steps in the the process will be
• Follow-up with Thank you notes (ask for the interviewer's business card)
• Follow-up with a phone call if no answer or update within 7 days of the interview

Don'ts:

• Be late. Excuses at interviews demonstrate a lack of motivation
• Give them any reason to eliminate you from consideration
• Oversell yourself or embellish
• Act over confident or be cocky
• Eat "smelly foods" the day of or the night before an interview
• Make inappropriate jokes or use foul language
• If you are interested in the opportunity, DON'T walk away without letting the interviewer know that you are interested