*Find a student-run club that sounds cool
*Figure out where they meet
*email the club president, ask if it's cool to hang with them
*profit

I'm a theater person, so improv would be where I would ask.

*Seriously, the lecture thing. Find a crazy physics lecture, grab a notebook and pencil, and sit there and act like this is the first time you've ever been to lecture. Try and make friends witht the person next to you. Bonus points if you take a test.

*Bring a football/frisbee/soccerball/hackeysack/cornhole thing
*Find a courtyard
*Set up cardboard sign that says "Come play football/frisbee/soccer/hackesack/cornhole"
*Wait for people and play fun sports games