As far as vetting, we use a 10-point system when vetting contractors to look for any red flags: check contractors state licensing board, get copy of GL & WC insurance certs, call their insurance agent, call references, check online reviews, interview the owner/manager, run background check, etc.

As I continue to interview contractors or potential architects for an actual quote.

I would interview lots of property managers.

Regardless of how you find them, try to interview at least three managers1.

Once you get this straightened out, interview a few PMs and hire one.

Try interviewing other agents in the area and see if they have a similar system. 

After screening potential tenant candidates,do you interview them and,if so,what do you ask?

As noted, I would do a full lease audit on each tenant, as well as tenant interviews. 

Interview your brokerages.

I am actively interviewing, and cannot wait to partner with a team.