How do I find a great mentor?

[Timothy Ahn]

Hello Bigger Pockets,

I recently listened to Episode 373 of the Bigger Podcast and have been inspired to take their advice to intern as the best way to learn and grow from more experienced mentors, while hopefully adding value to someone else's business. 

While I plan to research and look for a mentor, I wanted to know if there were some best practices for finding a mentor, how to approach a potential mentor, and what would be some key indicators of a good mentor? Also, what can I do to make myself more useful to my mentor in the mean time?