Some classes will offer automated waitlists through SPIRE while others will not. The decision is up to the department offering the class. Some departments prefer a first-come first-served approach to letting students find seats that have been vacated by other students dropping the class. Others maintain manual waitlists collected before or at the first class meeting. If you find during your initial appointment that a class you are interested in is full, you are advised to enroll yourself onto the automated waitlist if one exists (you can tell because the class will show a non-zero waitlist capacity in the SPIRE Schedule of Classes), or wait until the start of the term approaches to see if new spaces are freed.
If you want to enroll yourself onto a SPIRE waitlist, follow the instructions for adding a class and select the "OK to waitlist?" checkbox when it appears. There are some things you should know:
You will be assigned a position number on the waitlist, but departments and instructors may exercise their own judgment in altering students' positions on the waitlist. A position on a waitlist indicates a possibility, not a promise.
To get on a waitlist or to be moved off the waitlist into a newly-freed space in the class, you will need to meet all eligibility requisites like "seniors only" or "majors only". You will also never move from the waitlist to the class if the move would cause a time conflict in your schedule, if you are fully registered into another section of the same course, or if you are already registered for the maximum number of credits in your unit limit!
Students still seeking admission to a full class after classes start should attend the first class meeting and follow instructions from the instructor or department about continuing to seek admission to the class. Once classes have begun, the department is in total control of which students, if any, will be moved from a SPIRE waitlist into newly-opened seats in their classes.