You can find them on the UCI catalogue, which is updated every year. There should be a schedule for each major (including the "specialized" bio majors like neurobio, genetics, etc.). For a direct link, check the "Academics" page under "Student Resources."

The last day to add or to drop a class is generally the Friday of Week 2 of each quarter. If you want to add a class and are on the waitlist, it is recommended to attend the lecture anyways so you don't fall behind.

This is a tricky one. It's normally best to wait until the syllabus is posted on your class website (you can find the website on websoc.reg.uci.edu or eee.uci.edu). Professors will describe any required materials there. They'll also mention it on the first day of lecture, but by then most used or discounted books may be snatched up. On the other hand, don't buy textbooks too early. Bio classes have been known to switch textbooks from quarter to quarter, and you wouldn't want to end up paying for something you aren't going to use.

You can find it on the UCI School of Biological Sciences website! For the direct link, check the "Academics" page under "Student Resources." Generally, you'll need to contact a professor (or more) you want to work with, either by email or in-person, so look early! There are other research programs you can apply for that will enroll you in bio 199 without this step, such as EMRAP or MICURAP. 

As a bio major, our curriculum is pretty standard (at least for the first two years). With that said, there are some key things you should look for in adding next quarter's classes. These include required courses for your major, the time slot for both normal lectures and final exams (you want to avoid multiple exams in one day if you can help it), the teaching professors (some are good, others are great) and workload! Regardless of how (you think) others are doing, don't overburden yourself with too many classes. Anxiety and depression are serious but common issues on college campuses, so take note of your limits.