Build and treasure friendships -- real friendships -- with other female academics, especially those a few years further down the personal and professional road. 
[really large chunk cut out here because I realized in retrospect that I was lecturing, and thus burying the point in excess verbiage]
Of course you should have male friends and non-academic friends (as many of the latter as you can get). But other women in the biz know how the personal and the professional overlap and swallow each other and such in a very special way.
So, I guess this is really a mash-note to the lifeline that is a circle of lady-friends, a thank you to all you glorious, fun, irreverent, and really intelligent academic women, and a hope for myself that I can be a part of making things better for other women in the way you have for me.
Yours in sisterhood,
 Corollary: be open to being that further-down-the-road friend to others.