The best way to learn about people is to listen to them. I am concerned that if you just read a few books, you will get a limited amount of perspectives and bits and pieces of theories without the knowledge of how to apply them. If you don't have time to take a class in psychology, I suggest just keeping an open mind and being a friend.

If you did have time to take a single class, I would recommend a class on multicultural studies, through psychology, sociology, education, etc. That will give you the most benefit in working with the diverse groups (people who are different from you in some way) that you are serving.

Rap