There's only one way that's been shared with me:
Talk to everyone you know about what you're doing and go to every event where mentors will be. Eventually you'll meet the right one, one that takes an interest in your idea and gets excited by it. If you hit it off they'll invite you to continue the conversation in a more private setting (not a conference/event but maybe their office/lunch). You'll get together informally and casually and should do so without any pretense. If things work out you'll find the relationship develop to the point where you might even wake up realizing that you have a mentor.
Yes, it does sound a lot like picking up singles at a bar. Yes, adult relationships are like that. Go see "I love you, Man" and realize it's really not that different.
