So you landed the interview, did your company research, had great rapport with the hiring manager and breezed through the interview questions. You gave a proper, firm handshake, and left the interview feeling pretty good about yourself. Then they didn't call you, or a month went by...and they turned you down. What gives?
You should have written a follow-up note. Maybe you did, but it was a waste of their time, because it offered nothing useful, and was the exact note they've seen 1000 times before, so they hit delete without even looking at the name. Sending a follow-up note is expected. You're not leaping ahead of the pack by sending one, you're still in the middle of the pack. Hey, at least you're not the sickly, limping straggler anymore, right?
If you want your follow-up note to shine, and really make a good impression on your potential employer, you need to offer some additional value to your potential future employer. And if you need some advice on how to do so, check out this excellent article - page two even has an email template for you to start with. By showing your willingness to help solve a problem for their company, even before an offer is extended, you're bound to make a good impression. That was the whole point of your note, right?