Where to find a good startup mentor?

Dear reader, I read in a lot of startup books that the best thing to do as an inexperienced founder is to seek out a mentor that can give you valuable practical advice. They also state that a real mentor wouldn't ask for money because he/she would do it because they are passionate about it (even though later you might decide to give him/her something as a thank you note). Does anyone here has had this experience and can recommend ways on how to find and approach a good mentor? Any comments are appreciated.