If you haven't heard of Rate My Professors yet, you will definitely want to familiarize yourself with it soon. Rate My Professors is a website that allows students to publish reviews of professors they've had, enabling others to see how positive or negative their experience was. Users can search for UMass or a specific professor and read the reviews to determine whether or not you'd like to take that professor's class. This site has been extremely beneficial for me when I am choosing classes outside of my major, because I am much less familiar with professors from other departments.
What I find most helpful is that Rate My Professors allows you to see written comments on a student's particular thoughts and opinions on the class and professor. You can also see the student's rating of the professor's overall quality and level of difficulty on a 1 to 5 scale, along with an overall rating that ranges from poor, average, good, and awesome.
When choosing classes each semester, using this website as a resource is a great way to learn more about the teaching style of certain professors as well as the actual workload of each class. Since syllabi aren't availble until you have already enrolled and classes are about to start, it helps you know what to expect the class to be structured like and how much time it will take on a weekly basis. I highly recommend using this tool while picking your classes each semester.