Volunteers

Have a question for all you youth ministry gurus out there. (or just people with an opinion.)
First of all, I think we would all agree on how important volunteers to our ministry are. We need them, the ministry wouldnt work with out them, we need to appreciate them, encourage them, and so on.
There are too types of voluneers that I have questions for.

1. How do you deal with the ones who are negative?
From my own experience and other youth pastors, there are a few volunteers who always come up with the problem, but never really come up with the solution.
2. How do you deal with the ones who's behavior outside the church might be questionable?
Out of the two questions, to me this is the toughest.
If someone is a volunteer for your ministry and you hear about questionable behavior going on outside the church, but you dont know for sure, what do you do?
I realize the easy answer is to just ask them, but Im doubting they would be completely honest.

Just things to think about.