Having a good working relationship with you teacher is very helpful for doing well in their class.
Before you sign up for a class try and find out what kind of teaching style they use. Also try and find out how they interact with other students/people.

A good place to look for help for your “teacher investigation” would be your Student Support Services center. If this does not produce enough results, you can ask other students who have taken classes with the teacher you are inquiring about. Ask the students what they thought of the teacher.

It is very important when you are asking for information, that you already have your questions written down.
Your teacher is likely the one to be guiding you through a lot of difficult material. Make sure you understand their language and methods before jumping into their class.