This is a great question. Proper class scheduling is something that first-time college students sometimes overlook as they can be overwhelmed with the transition into college. It's important to keep in mind that the specifics will often vary by school. However, I will try to provide a brief guideline as to what a new student can expect.
To begin, most colleges will have an academic advising program that is designed to provide advice to students about what courses to take in order to remain on track to finish their degree on time. Therefore, it may be beneficial to check in with your school to see what kind of assistance they offer to students who need help selecting classes.
Usually, classes are available at many times of day throughout the week. Additionally, different formats are available in many schools. For example, an introduction to mathematics class may be offered on campus 3 days a week for 1 hour each day. In addition, it may also be offered in an online-only format which may provide more flexibility for certain college students. Certain class times and formats will be known to fill up before others so it is important to not procrastinate when it comes time to select classes.
In my experience, class schedules for the upcoming semester were available about 1 month before scheduling was to begin. This provides plenty of time for students to explore different scheduling options. As mentioned above though, many classes are prefered by the student population and are likely to fill up quickly. Therefore, it is important to have alternate classes and times planned in the event a particular course you wish to take is filled before you can schedule.
While it may seem overwhelming the first time you see the entire list of courses being offered for a semester in your school, it's important to remember that for many students, the first year or two of college mostly consists of general education courses (math, science, writing, etc.) that are often designed to accommodate large numbers of students. This lessens the chance that you won't get into a course that you are planning for. Additionally, once you decide on a major, there will be certain courses that are required in order to graduate. This provides guidance to make sure that you are accomplishing all of the necessary courses in order to graduate with a particular degree.
Hopefully this helped give you an idea of what to expect. Good luck.