regards to "4. gut feeling during face to face interview", it's good idea. however it's hard to do so if you remotely manage your properties. In this case, I would rely on my crew who shows the property to give me some his impression. Just make sure they are clean people.
Even thought you don't see you tenants, which is my case, I observe their behavior, the way they talk, and any follow-up action as they promised.
