Choose a supervisor who makes you excited about your project. There will be times when your project does not go as planned and reminders of that enthusiasm and why you are doing the work are crucial to continuing through the hurtles.
I believe that one of the keys to success in terms of graduate studies and beyond is to be passionate about your work; this makes the dedication required to do well come that much easier.
I would tell any prospective grad students to visit the campuses they are applying to, and talk to students in their program(s) of interest! A major factor in my staying at Guelph was the campus community, and knowing that I would be supported throughout my studies in not only my academics, but also through the social atmosphere on campus.
I came from a small town, so when I first moved to Guelph I was kind of intimidated by the transition due to leaving a rural area to come to a city. I have lived in Guelph for almost eight years now and even though it is a city, it has that small town feel which I like.
My advice would be that a Masters degree is like a roller coaster. You will have your ups and downs in your research but that is all apart of being a scientist! There is no such thing as a 'bad' discovery.
Words of wisdom for someone considering grad school...
My advice would be to not be afraid to try anything. Take any opportunities you have for new experiences because you never know what you will end up liking! If I had not tried a wide variety of courses during my time at the University of Guelph, I would not have discovered my interest in reproductive biology. Also, take any opportunity you can to speak with other graduate students; everyone is extremely friendly and always willing to lend a hand if you need it. Your peers are a great resource and are always willing to offer some advice on school, research, or life.