1. Learn to backpack. It is super-cheap to hop on a RyanAir flight to almost anywhere in Europe, but only if your luggage consists of one carry-on bag. Learn what you need to bring for a weekend trip, and what you can leave behind. (Hint: you will want a water bottle and a rain poncho much more than your laptop.)
2. Learn about football. Not American football, but that sport that we call soccer, and everyone else calls football. The one where players actually use their feet. If you are sporty, learn to play a little. If not, at least learn a bit about some of the teams and players in the English Premier League. You will have a much easier time making friends.
3. Get in shape for hiking. You should put a lot of miles on your sneakers exploring foreign cities. Might as well start practicing now.
4. Do your homework. Don't end up at a bad school, or one where you can't take classes that transfer back to your home institution.
5. Do your homework. It's fun being someplace where you can drink at 18, but don't forget why you came here. It is important to strike a balance between having fun and getting stuff done.
6. Never use your credit card to pay for a phone call, even if you have to spend the night in a bus stop in Madrid. Carry a phone card so it isn't an issue.
7. If you go in the fall, you can watch OU football on
P2P4U.
8. Get
skype. International phone calls are expensive, but skype is a free program that lets you talk to people all over the world for free. It even has video chat, if the internet in your dorm is reasonably fast. You still need to figure out the time difference, though.