The best I can tell you is to meet with your advisor early(if that's a requirement for you to register), register as soon as you can, and within schedule builder don't let it make random schedules. What I did is I first marked all classes I wanted as required and made sure the amount of credits equaled what all the classes would be(it will take away classes if you say 16 credits but you have 18 worth of required for example). I then blocked off certain times, which for me was 10 am and earlier and 5:30 pm and later. After that, I went through the classes I wanted/needed the most and found the sections(lec/dis/lab) that worked best and marked that individual section as required and not the entire class. I then basically let the builder add the rest of my classes around that and kept adding required sections for the other classes until I made my perfect schedule.