These guys are amazing: https://www.turnkeyvr.comThey utilize the latest technology such as Ring doorbells on your property (can see if unauthorized guests are at front door or huge party being thrown w/our permission), and iPad setup inside with local available activities listed for guests (which btw also has a hidden decibel reader so they can detect unusually high noise levels in your home).

Then one day my phone rings at 5 am!

Be ready for the phone to ring.

In addition, I am finalizing yellow letters to send to FSBO.I need suggestions to make my phone ring.  

In homes i've worked with in the past I usually skip trace the next of kin, then give them a ring to see if they can get all the decision makers for the property on board to have a conversation with me! 

My phone did not stop ringing for 2 weeks!  

And if it turns out you've made a mistake on a tenant, the legislative headwinds make it very difficult to un-ring that bell and terminate that business relationship. 

Is there any evidence that one is better than the other to make the phone ring?

I'm putting together a direct mail campaign targeted at homeowners who are in preforeclosure and could really use some insight.My thoughts are that 2500 6x11 postcards monthly should be enough to get the phone ringing.

Persist and your phone will ring one day.