RfA grading is a simple tool I use on Wikipedia:Requests for Adminship. I give each user points for different things on a weighted scale, and give an overall grade. For example:
RfA Grading: RfA grading
Need for Tools
5/5
Interaction with Users
20/20
Edits
15/15
Other
10/10
Total
50/50 (100%)
A