I've had 5 job interviews. I was successful in 4 of them.
The only one I wasn't successful with was a science teaching job on the local army base. I knew the person who got the job. She actually majored in a science (I'm a math major), plus she's in the army reserves. I didn't feel bad that I wasn't picked.
what's your secret dude?
Know a lot about the company you're applying for before the interview. Casually bring up things you know about the company during the interview (ties in well with answering the classic "why do you want to work here" question). Have a bunch of relevant work related stories to connect with during the interview.
These worked for teaching jobs. My other 2 job interviews for less serious positions were mostly a personality check to make sure I wasn't a moron.