Request courses at a variety of times. This will increase the likelihood of getting courses that you request, since the system won’t register you for two courses scheduled for the same time. If you’re a morning person, keep an eye out for 8:00 or 9:00 am sections. Those tend to draw fewer requests and may be easier to get into. The same is true of evening labs.
Many courses have labs, discussion sections, screenings, or tutorial times to supplement the lecture portion of the course. You should assume these are mandatory and plan around them. You'll be able to tell if your course has additional "activities" by clicking on the course listing in Class Search, bringing up additional details about the class. In the upper left corner will be a list of the course components (e.g. just "Lecture" or "Lecture, Tutorial").
Scroll down on that page to see details about those supplemental activities.
Select more options than you think you'll need. It's absolutely critical that you submit backup options as part of your course requests. You may not need them, but you'd much rather have them unnecessarily than get stuck with a course conflict that can't be resolved based on information you submitted.
For courses like Humanities and Social Sciences, you’ll increase the likelihood that you end up with a schedule you're happy with if you select multiple courses as well as multiple sections. That might mean choosing a Tuesday-Thursday section of Readings in World Literature and a Monday-Wednesday-Friday section of Human Being and Citizen, for example.
Don't be afraid of scheduling courses back-to-back. There is a 10-minute window between courses, and this is enough time to get from one classroom to another.
Be aware that while the class schedule may currently show that many SOSC sections are full, we reserve some seats in each section for 1st year students. This is an unusual case where you can still plan to request the course even if it appears to be unavailable over the summer.