Many studies have shown that official mentoring programs increase the retention rates of women in the sciences (as students and as faculty). AWM has a mentoring program that you can join if you're interested AWM. I think informal mentoring relationships are also very important.

Definition: Mentoring is defined as significant personal and professional assistance given by a more experienced person to a less experienced person during a time of transition.

(Quoted from an article on the Women in Engineering program at Purdue which appeared in Anchora of Delta Gamma. My mother showed this to me because I used to teach at Purdue.)

Who? (People who may be mentors, even if you don't think of them that way.)

Other students
Faculty (not just your official advisor)
Colleagues you meet at conferences
Seminar speakers

When? (Times when I especially recommend seeking out mentoring.)

When choosing a field to concentrate on
When choosing an advisor
When applying for a job or grant
When deciding on a job
When you want to find out about conferences in your field
During office hours
When working on homework or research together


Everyone can benefit from having role models
Misery loves company (This was the slogan for an undergraduate women in science group I was in)
To develop relationships now, so that later it is easier to:
Find people you can discuss mathematics with (even when you're afraid your questions are too simple)
Find people you can do mathematics with (future co-authors)
For reference letters