I've been flipping through Peters' book on graduate school and realize that it's imperative that I find a good advisor in my master's program so I can have a solid LOR for doctoral studies. Now, I have this feeling that unless I'm the top student in my class, I cannot approach this one professor, who is tenured and busy, yet known for being a helpful mentor. I did do well in his class, but I don't feel confident about myself. How do I approach this professor to either conduct an independent study under his mentoring, ask him to support my master's thesis, or ideally, work as his research assistant?