We can't give too much away because that would ruin the surprise on Doolie for a Day (the cadre did not let us see the schedule at all), but I can give a few hints.
1) Give 100% effort and support your element completely on Doolie day. You are only as good as the weakest team member, so if someone is struggling, HELP THEM! We literally pushed a few team members up a hill during running and we all felt great afterward because we used teamwork to make it.
2) PT is challenging, but not too bad. The cadets understand that we are not acclimated.
3) Ask all the questions you possible can. The cadre are AMAZING and have really great advice and personal experience stories.
4) Start learning the "mini contrails" immediately. You need it memorized for Doolie for the Day. My roomate and I quizzed each other every night, and we were fine.
4) You are only allowed to wear the issued clothing (shorts, t-shirts, cap, polo, jacket), so the only clothing you bring that you wear is kaki pants. I'd bring at least 2 pairs (if you are on the parade field they get muddy). I'd also bring some undershirts to wear under the polo. We all wore tennis shoes the whole time, so dress shoes really aren't necessary.
5) Make sure you have LOTS of extra room to bring home issued stuff. I brought an extra duffel bag, and that worked fine.
6) Because it was raining when we arrived for session A, we never got a tour of the academy or a chance to visit the C-store. Thus, I never had a chance to spend any money. You probably don't need that much.
7) Have fun! I had a great time, reinforced my desire to attend the academy, and met some great people. Summer seminar was an awesome experience.