De Anza offers students the ability to add courses prior to the beginning of the quarter. As a result, you may find that the classes you want/need are full of students and that you cannot add the course.

The first step is to add yourself to the waitlist via the registration system.
The next step is to attend the course that you want to add. Identify yourself to the instructor as wanting to add the course.

If the course is very popular, then there may not be any seats available. You may be told by the instructor to leave and try another course. Go back the next day! Continue to go back and stay until the instructor tells you to leave. By the end of two weeks, there will be open seats. If you fail to attend every class, then the instructor may claim that there were students there before you and it wouldn't be fair to them to add you in front of them. Therefore it is imperative to attend every class and ask for an add code each time.

The higher your unit count, the sooner you will be allowed to register for classes. Also, some programs will provide priority registration. As stipulated by law EOPS, Veterans, and DSS register before all other students. Try to find a program that will qualify you for priority registration.

There aren't seats every time even if you wait 2 weeks. I've been in Japanese classes where no one was added all quarter, despite the teacher saying to wait. As well as other smaller courses like astronomy. You aren't always guaranteed to get in if you wait 2 weeks. If you can't get the classes you need, you can always go to Foothill College OR each quarter, your registration date does come earlier, so you eventually get to sign up before others (this is based on how many total units you have).