Largely what you'll do depends on how much of a time commitment you're willing to make. Ideally, you would do something like learn Spanish if you don't know it already, move to the border, and do rape crisis work for all the women who have been raped by men patrolling the border as a result of increased militarization.
But that's a lot to ask of you.
Know your local resources - rape crisis centers, DV/abuse hotlines, reproductive health clinics, women's shelters, all that jazz. Share this information with those who need it. Be able and ready to help women who ask - make yourself available to go with a friend to get an abortion or a pelvic (and make sure in advance that they know that you will do this if they ever want.) Know where further information is for women in need of it. (Know about sex ed sites especially.) Try to be someone that other women can come to if they have been raped or otherwise need help, if you are prepared emotionally for that yourself. Volunteer if you can, somewhere, as a Big Sister or in a senior center or at one of the myriad things they surely have in your college.
Speak up, firmly and calmly, when you hear someone spouting anti-woman or anti-feminist bullshit. If they want to fight about it, you don't have to let them. (You can usually just walk away.)
Educate yourself. That's how you learn to recognize anti-woman and anti-feminist bullshit in the first place. Just keep reading, and reading, and reading.* Take some courses on women's lit, or the psychology of gender, or whatever your college offers on the subject. Read some blogs. Donate monthly to your favorite.
Live feminism. Love your body, and be vocal about it. Break the silence about all the harassment you've experienced because you are a woman. Start discussions. Be a mentor to the young girls in your life (little cousins?) and compliment them on their accomplishments rather than on their dresses. Take back the night. (You don't have to do that alone! We have rallies!) Eat in public. Eat lots
in public. Don't be ashamed to take up space. Don't take less than your fair share. Make yourself visible! In whatever you do, odds are women are underrepresented or undercredited or both. Simply by gaming/being on the internet/joining your hall council/doing activism/most things as a woman, you're raising awareness of women. I know it sounds silly, but in a culture where male is default and female is other, people will forget women do these things if you don't remind them.
Practice affirmative action on your own. Buy books by female authors and music by female artists. Read poetry by female poets. (*coughs, points to signature*) All else being equal, vote for women.
But it all comes from educating yourself. That's the most important thing. Keep learning and learning and learning, and that, I think, will naturally lead to action.
*If you want a few things to start out with, here are a few links. Dunno if you've gone through all the finallyfeminism101
posts, but do that, and not just the FAQs either. Melissa McEwan at Shakeville also has a feminism 101 series.
Tekanji at Official Shrub
has done a lot of work on privilege (including intersectionality) - I recommend everything on the sidebar at the right. Also look at everything on the sidebar at Bitch PhD. The Hathor Legacy
is a great resource for critiques and discussions (don't skip the comment threads!) of books/movies/TV shows/etc. Guttmacher
is priceless - read especially everything they have to say on abortion.
There, you won't get through all those in a day; and if you're like me, it'll take you on a wikipedian-style neverending linkfest adventure.*waits for everyone to focus on one single sentence*
Raise up the torch and light the way.