rush week

You'll get a lot of this information during Fall Formal Recruitment orientation, but I'll give a brief run-through.
Basically what a visit to a house consists of is talking to various women in each house - you're trying to get an idea of them, and they're trying to get an idea of you. There will probably be a skit, a song, or a presentation of some kind.
The first day is Unity Day, which focuses on being Greek in general. Every sorority woman will be wearing the same Cal Panhellenic shirt. You'll visit all 13 houses.
The second day is House Tours, during which you receive full tours of the physical houses. You'll visit up to 10 houses.
The third day is Philanthropy Day, during which each house will provide a presentation on their national philanthropy and their on-campus efforts to support it. You'll visit up to 7 houses.
The fourth day is Preference Night. Each sorority will have one last presentation showcasing their house, and you'll hopefully be having the deepest and most meaningful conversations on this night, since this is the last chance you have to get to know members of these sororities before one of them becomes your sisters. You'll visit up to 3 houses.
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...After Preference Night, you rank the 3 houses you visited in order of which you'd most like to join. If you rank every house you visited as a house you would accept a bid from, then you are guaranteed a bid the next day. If you don't list every house you preffed, you can still receive a bid, but it is not guaranteed. When you arrive at Bid Day, you will receive only one bid, and that sorority, if you choose to accept the bid, will be yours for the remainder of your Berkeley career.
Throughout the recruitment process, PNMs and sororities participate in a mutual selection process that determines which houses you visit the next day. Sometimes you visit houses again you originally wanted to drop, sometimes houses you liked don't ask you back, and sometimes you have fewer houses on your schedule for the day than someone else. That's all okay and normal. I had all of those things happen to me during my Fall Formal Recruitment, and I still couldn't be happier with my experience in the sorority I ended up joining. My advice to anyone reading this is to stick it out through FFR, even if it's frustrating or disappointing or stressful for you. It's one week out of four years, and the Greek life experience is worth the headache that recruitment can be for some people.