Another thing to add to the excellent list above is making embarrassing offers.

I was planning on sending oversized postcards (but being discreet about the services as not to embarrass or announce to everyone they were in foreclosure), sending personalized letters and postcards via Priority mail overnight envelopes, and doing some of the plain-Jane approach.

Maybe they didnt even acknowledge you cause your offer was so embarrassingly low, they were actually offended.

I'm embarrassed to say but I'm a bit scared of fixer uppers.

Instead of raising hell and with the terrible feelings of shame and embarrassment I did not complain to any of the authorities. 

If you are not embarrassed about the amount or terms you are offering, you are offering too much!)

No matter how good your rehab is, a good inspector will find issues when your buyer has their inspection (he'll make up issues if he has to, as it's embarrassing if an inspector can't find anything wrong), so expect to spend money after the rehab is done as well (add $1000 to my worst-case budget).When I started, my worst-case budget was always about $10-15K above my target budget.

It could make your relationship a little uncomfortable but I think your tenants should be the ones embarrassed and worried about damaging the relationship since it was their bad.

Have been in real estate since I was 15, helped build some brokerages, businesses and buildings and to my embarrassment took forever to finally join you fine folks here on bigger pockets. 

I'm kind of embarrassed I'm twelve years late to the party, but here we go!