What's the best way to break up?

The ideal way to break up is if it's mutual. Breaking up sucks no matter how you word it. Someone is always going to get hurt (typically) more than the other. I would suggest trying to be as nice as you can about it. Say you're still trying to figure out what you want out of life and you need some time to yourself. She'll probably still be a little mad, but at least it doesn't sound like you are closing the door forever (even if you are, you don't want to come off that way).

The best way to break up with someone is in person. Be honest, and explain why you want to break up. If a guy broke up with me I would be crushed, but I'd understand, allow myself some time to get over it, and life goes on. I'd still want to be friends, I wouldn't want to get back at him in any way, and I'd wish him luck with his next girl. Breaking up is hard on both the guy and girl, but being totally honest with yourself and her and doing it face to face is the best way

The BEST (but maybe not the easiest) thing to do is be honest with the girl you are breaking up with. There is NOTHING more frustrating than a guy that is clearly using lines to try and not hurt your feelings. We know you are lying and then we will hate you even more. If you just don't have the feelings anymore, tell her! No break up is easy, but honesty is always the best policy. She will be able to move on much more quickly if she knows you broke up with her for the right reason.