re: Any tips on Firing someone?

You owe it to them and yourself to be as direct and to the point as possible. Do not drag it out, it never helps. Don't make it personal, even after they make it personal, it's not worth it.

If possible, I would have someone there as a witness. It makes it odd for a moment, but it keeps everyone (fired employee) in check, and eliminates problems later.

Everything I just said I learned from doing it not in this fashion before. It's never easy and you should be glad you are having a hard time with it, means you may be human.