Some really great questions to ask him are :
How many rats has he lost on the table?
How many neuters has he done?
What sort of pain medication do they use, and how do they administer it?
[ie: do they give a shot of metacam pre op, and then give you metacam to take home post op]
Do they give Baytril after surgeries, or are willing to give it as a preventative?
What sort of sutures do they use?
How does he do the actual procedure?
[Don't have boys, so I can't remember the actual names. I know one's through the testicles, but the other...]
That would be the nice long list of questions I forgot to ask when I had my first girls spayed. Would have saved me alot of time and effort if I had.