frozenrope-
We simply evaluate the kid 1-5 like the rest. However, we also have an area for individual spontaneous comments by the coaches and we always meet at the end of tryouts to discuss the cuts as a staff. We hole up in my classroom and go over every kid (after we place the "automatics" on the team - no sense wasting time) thoroughly in every area we can.
We rate his skills, but we also discuss what we see from each kid in terms of: listening/coachability, intelligence (grades in school are posted), previous coaches' comments (from as many as I can find), ht/wt, ceiling as a player (if not a senior),etc.
I have subscribed to the Bobby Knight rule (no jokes about the last name, please - and I think he's a classless putz despite his genius!) about cutting. I keep the 12 kids or so that I can see really fitting into the rotation in some way, and then I fill the rest of the roster with guys that are either projects or one-talent guys (speed, developing pitchers, bunters, bullpen catchers, etc.). I have found that the biggest pain in the butts are NOT the kids who sit at the end of the bench...the problems come from the kid who thinks for whatever reason that he should be starting. This was B. Knight's idea, and it has worked for me over the years.
Be honest with the kids upfront as to what you are doing, and make sure every coach in the system is 100% on board with it.