The interview is over. How do you feel about it? Did you prepare sufficiently? Did you research the company so you could be reasonably conversant on the products or services? Did you find out who you'd be talking to and look for them on LinkedIn to see whether you have connections, schools, or interests in common? Did you handle the questions well because you checked out the tough interview questions? Were you able to ask a couple of intelligent questions about the company and its industry? Great!
BUT YOU CAN STILL BLOW IT IF YOU DON'T FOLLOW UP!
It seems incredible but my daughter Meredith reports that about half of the people she interviewed for an entry-level job never sent a thank you email or note. How insane is that? They couldn't take the five minutes to write a simple note to the person who scheduled the interview, or the people who interviewed them, saying "Thanks very much for the opportunity to meet today. I appreciate the time you took to explain the job and it convinced me that I would enjoy working with you and the others I met. I think I have exactly the qualifications and attitude to succeed at XYZ Corp. Please contact me if you have any other questions. I look forward to hearing from you."
Don't be that person. Send a thank you email. It's an easy way to differentiate yourself from the clueless.