If you're really good, your boss is going to do everything they can to get you to stay. This is great advice on how to leave as quickly and painlessly as possible.

I usually thought that if someone is interviewing with you they probably made up their mind on quitting their job, so I didn't push it at all. But I've seen this happen, where it ends up taking 3 or 4 weeks because they're finishing up a project. I'm glad they finish what they started, but its true, I probably could have used them yesterday.