I'm not sure where you live or where you plan to go to school, nor should you advertise it here or anywhere else (repeat after me, "Discretion is King"), but in addition to the above, work on:
-Conversation Skills. You will need these the rest of your life. Learn to talk to little old ladies as you kindly ask them to give you recs, to children whose parents may help you, and to those your own age of all cultural backgrounds. Be ready to talk to anybody!
-Learn your best looks. If you plan to spend a lot of time at the beach, condition your skin and hair so you don't prematurely age yourself. Diet if you need to do so, no matter what, get toned. Learn what kind of makeup you can wear without lookly like a skank, even if it means making a few trips to some Clinique or other makeup counters.
-Learn your best dressing styles. This will be an evolving process for the rest of your life, but you can't go wrong.
-Check out the websites for every sorority that will be on your campus. You can usually find most of these with
www.thesororityname.org, or just google them. You don't want to parrot this information back to sisters during Recruitment, but you should be at least a little knowledgeable about each. Know that Mu Mu Mu's philanthropy is The Home for Reprobate Actors, their colors are Puce and Tie Dye, and their most famous alumna is the Coat Room Lady at The Billy Goat Tavern, but if you "overlearn", you could be labeled as a stalker. However, if you know a Mu Mu Mu, it would be odd if you didn't know that.
-If you know anyone else who plans to go through Recruitment, practice with her. Practice smiling when your feet are killing you, sitting gracefully in each outfit, laughing naturally, and conversation, conversation, conversation!
-Check out your school's website for Greeks, and especially check out the dress suggestions. If they say "shorts or jeans", go with the dressier. Make sure you can sit, stand, and walk gracefully in whatever you wear. You may want to think about a white dress (many sororities use them at some point, and you'll never find one in November!), and a good dress for Pref. Don't forget that you're dressing to impress women, not men! Ask your friend to vet your wardrobe.
-Recs, Recs, Recs!!!! Get an HONEST resume ready to hand the nice alumnae who will give you a rec, and buy some nice note cards. You'll want to send each of them a thank you note after they interview you, and also a note to let them know that you a) dropped out of Recruitment, but thank you; b) you accepted a bid to a sorority other than hers ("but they were lovely...") or c) you accepted a bid to her sorority and you couldn't have done it without her! Yes, it's bull, but it's also life.
-In between, work, volunteer, and/or enjoy your summer - you will need something to discuss when asked, "how was your summer?" Saying "I hung around" just doesn't cut it.
I had no idea I'd go on this long, but I think you get the idea. Keep an open mind and best of luck!