If your friends are all wearing City Sports t-shirts, buy a City Sports t-shirt. You are, as a freshman and right out of high school, most likely a stranger in a strange land, and it won't hurt to blend in as much as possible. If you are planning on joining a fraternity, start investing in Ralph Lauren.
Get a fake ID. Get a good quality one that scans and blacklights, which will set you back around $120. You will need it to get into the clubs and bars around Philadelphia.
Keep your room clean. If you can, stack your beds. It's hard to socialize in a small room.
Buy alcohol. You will be popular with your friends if you can supply alcohol to them.
You will always be able to do schoolwork. Go out.
Be generous with your money. If you have money (and if you go to Penn, I am guessing you do).
Smile. Nobody likes a grouch.
Enter your room with a purpose: Use your room to change clothes, to pick up or drop off schoolbooks, to sleep, to drink with your friends, and to hook up with sloppy drunk chicks. You will not be social in your room.
Get off your damn computer. If I had a nickel for every hour I spent checking Facebook, or walking by people's dorms seeing them staring at their computers, I would be rich enough to donate a building.
Don't eat alone. Going down to the dining hall and trying to find people doesn't count. Meals are a great time to catch up with people that you don't see every day.
Make your habits social habits. If you really like playing basketball, find friends to play basketball with. Reading and playing online poker are nice habits but you will not make friends doing them. Then again, I write a blog and have Google Reader as my homepage.
Liked what you read? I am available for hire.