Make sure to visit the beautiful campus - a natural haven of streams and eucalyptus trees.
Also, take advantage of the myriad dining possibilities -- almost all the restaurants are cheap, fast, and delicious.
Quick Tips:
Get used to the idea of lots of people asking for money -- regardless of how you feel about it, it'll happen frequently.
Get an enormous salad at Intermezzo for .25
Take a tour of campus if you're interested in the school.
Best Way To Get Around:
The easiest way to get around downtown Berkeley is by foot. If you want to head into San Francisco, then the BART will get you there in a half an hour for about .75. For downtown Oakland or North Oakland, the bus is cheap and efficient.