Although you may think that simply liking the type of research a professor does is the only criterion for picking a graduate supervisor, there are actually many more things to consider.
Take a look at www.phds.org for lots of good advice on getting into and successfully completing graduate school!
Other things to look for in a Master's or PhD supervisor:
1. A good mentor. A mentor is someone who guides you through your degree and will give you the kind of advice that's hard to find on the web or in a book. Everyone (including professors) need good mentors to get us to where we want to go.
2. Someone who will meet with you regularly. It's very important that your supervisor will make time to meet with you to discuss your experiments and progress. Principal Investigators (PIs) are very busy people and not all of them are willing to take time for you.
3. Someone you get along with. You will be spending a lot of time with your supervisor and you want to make sure you are a good "fit" with their personality before you sign on. Make sure you talk to the current lab members! This is very important to get the real scoop on what your supervisor is really like!