The obvious place to start is here:
http://www.music.unt.edu/percussion/resources.htmlCheck out the Barrier requirements so you can at least be familiar with the material and know what will be expected of you.
Get in touch with the teachers there and try to visit as early as you can.
See about getting a lesson with Ed Soph to see how he does things, and if you feel like you'll enjoy studying with him for 4 years.
When I picked my school I didn't
really know what I was getting myself into and realized too late that I should been more careful in my decision. Don't get me wrong I went to a pretty good school and had some great teachers... they just weren't into the same things I was and I would've benefited more at a school that was more geared to what I liked.
UNT is a great school and obviously if you go there you'll get a world class education... but just make sure it's the right fit for you.
My original plan for graduate work was to go to UNT but now that I know little more about the academic music world and what my goals are, UNT just isn't the school for me.