Hmm... you just have to be interesting to me. Well-traveled, or intelligent, or passionate about a cause, or able to tell me more about areas I'm not familiar with. I love people I learn from.
...oh and, if you send me a friend request, please also send me a message explaining why... if I know you, I don't want to overlook you, and if I don't and you can't be bothered to make that effort, then I do I really want to be your friend? ;)