Pass 1, Pass 2, and Open Registration
These are the periods when you can register or drop your courses. You can register courses of 17 credits after beginning of Pass 1, 19 credits after beginning of Pass 2, and 28 credits or more (more credits need to be applied to the official) after beginning of a quarter or semester. Some courses are limited to certain majors and can be only registered after the beginning of Pass 2.
You can check Pass 1, Pass 2 time through your own UC Davis account on myucdavis or Schedule Builder. You will also receive reminder from UC Davis through you school mail account. You can register or drop courses within four hours after the Pass time begins. Open Registration time can be viewed on UC Davis Official Calendar, which you can register or drop your courses 6:00 a.m.–midnight in weekdays and 10:00 a.m.–6:00 p.m. in weekends.
Suggestions on course registration
Better to register course you want the most in Pass 1. There's no guarantee that there will be new seats added in Pass 2. You can view your major requirements on UC Davis Official Website. There's also GE credit requirement, which you can view when you do First Year Aggie Orientation.
You'd also better view prerequisites of the courses before your registration. If you don't fit the prerequisites, you will be asked to write a prerequisite petition, which will ask your confirmation when you register the course! (I missed UWP 007 course in the first quarter due to a few seconds delay caused by this)
You can do advising appointment to ask for help to select your courses through UC Davis Advising Appointment System. (Which also includes tutoring on different classes)
There is "Pre-Check Registration" and "Register All Changes" button on the top of Schedule Builder Website. Do not register the courses one by one, and again if you have prerequisite petition, there will be a confirmation when you register the course!
There is "waitlist" in course registration. You will be asked to allow waitlist if there's no seat for the course you want to register. Usually whether to register in the course successfully is based on the professional level and size of the course. Lower professional and larger size means more opportunities. Other students usually drop their courses after quarter starts so be patient with you waitlist. Waitlisted courses will also be counted in the registration credit limit so be careful about your selection.
Same course or time conflicting course can't be registered at the same time.
Some courses have paper text books, which you need to get in Memorial Union.
Example of Schedule Builder
(Very pitiful schedule, isn't it?)