Everyone agrees that it is important to examine the faculty at different schools before selecting a graduate school program. Unfortunately, "everyone" frequently agrees to things like this without telling you how it is that you are supposed to accomplish this monumental task, or even why they agree in the first place. Hopefully this article will help think through these questions.
First as to why faculty is important: if you are earning your master's degree you will be spending one to three years (and much longer for a doctorate) working with these professors. It is therefore important that they be people with whom you can work. It will be important to establish a positive relationship so you can always be in tune with your expectations and performance. Further, you will want to find faculty with similar research interests to your own. Assuring that you have similar interests will likely facilitate finding an advisor, as your common interests will encourage a positive working relationship. So obviously, the 'why' part of our question is not rocket science.
But having determined 'why' you still need to answer the question of 'how' to learn about the faculty at different schools. Many schools actually have some of this information on their websites or in brochures or department publications. They may provide short biographies of their professors including published works, and research and teaching interests. You could read something they have published and determine if the interests they are pursuing would mesh with your own. (This of course requires that you have done some serious thinking about your own interests and reasons for pursuing a graduate degree first!)
However, there is only so much you can learn from reading about a person. Networking should be a vital part of this process as well. Talking to other graduate students can yield a great deal of information. Students who have worked with particular advisors can tell you about their personalities and how it was to actually work with those people. Ask about the advisor's style - does the person like to meet frequently or does he or she prefer to have the student take a more independent approach? Is the advisor more likely to develop individual topics with students or hand out ready-made topics? Other students who have actually worked with these advisors should be able to answer these questions for you, but it still remains for you to decide your personal preferences. You may prefer an advisor who is more involved or you may prefer to be left on your own and have someone who is there to answer questions when you need help.
Further questions you need to ask may be: What is the average length of time graduates need to complete a master's or PhD? How many students drop out? How long has this person been an advisor? Once again, different people will want different answers to some of these questions. What you need to remember as you are exploring your options is to be examining your own strengths and weaknesses and your own needs as well as those of your prospective advisors.
Another good way to learn about the faculty may be to contact them directly. Many of the websites you were looking at earlier to determine research interests may include contact information as well. One method of contact that is fairly non-obtrusive could be a simple, friendly email. You could inquire into their current research projects or any supplemental information about the graduate program that they feel you should know. This may lead to an extended discussion or may not, but at least you have made the effort to introduce yourself and expressed your interest. Further, if this professor is involved in the admissions process, it cannot hurt if he or she has at least heard your name before and seen your pro-active approach.
Having examined yourself and the prospective faculty in the program or programs to which you are applying, you should have a firm foundation and the knowledge you need as you enter the application process. Don't forget that this information, and effort you have put in, can help you in writing your application essays as you highlight why you would be the perfect fit for a particular program based on your interests and the information you have gathered. So with all those preparations in place, there should be no need to worry. "Everyone" agrees.