1. Please please PLEASE dress appropriately. Khaki shorts, messy hair, and flip flops don't make a good impression.
2. Show up for the interview! Or if you can't make it, call and let us know why. We can always reschedule. But not calling or showing up will severely impact our decision on whether or not we will place you.
3. Don't give the front office person an attitude. She/he will refer everything to your recruiter.
4. Don't be late and then ask "How long will all of this take? Because I have my mom waiting in the car..."
5. Reading your recruiter's future during the interview? Probably not the best idea.
Yes, all of these things have happened. And more. I just wish I could remember all of them.