<p>I don't know how prevalent this it but our youngest had to pick up an important sequence class in drop-add because it was closed out during regular registration. Apparently this happens a lot, but everyone who is persistent ends up getting in. The reason is, 2000 people sign up for the next course in the sequence, but 200 or so will fail the first class (and get automatically bumped by the computer when the grades come in), or drop the second class because they got a C or D and are switching majors. Hence hundreds of students who got shut out during regular registration end up getting in anyway. It's kind of like what the airlines do in reverse- if they were to keep opening up sections for everyone who registers, they'd end up with hundreds of empty seats.</p>
<p>Another trick the students who have earlier registration times do is booking up classes for their friends during regular registration. They'll register for a class at a prime time, then make plans to 'drop' the class as their friend 'adds' it later on in the process. </p>
<p>Even another trick that REALLY messes up the system, is that students will overbook their classes, attend the first meetings, then decide which class on their schedule to drop, creating even more open seats by the end of the first week.</p>
<p>Many students just don't show up for the first class, and in the labs, the professors are allowed to automatically drop their names from the roster. It's commonplace for students to attend labs they aren't registered for on the first day, then get added to the class roster on the spot. Sort of like flying 'stand by'.</p>
<p>If worse comes to worst, they can contact the professor directly and many times he will pull strings and get them into the class.</p>
<p>The thing is, you just gotta be resourceful, ready to exploit opportunities, and persistent.</p>
<p>Then you have the students who just don't want to take a class at an 'inconvenient' time, so when they go to register and find out the only available sections are at 8 AM or on Friday afternoon, they wait until the next semester and get behind. Or students who get frustrated when they don't get in during regular registration, and just give up.</p>