If the blower wheel is plugged up full of hair, get an HVAC tech out to clean it.Go around the house to all of the air vents, and make sure the flaps in them are open (use the little handle/lever/knob that sticks out of the grille), and that they don't have a rug or furniture or something blocking them off.Sometimes people will turn the thermostat down and then close the vents to try to regulate the temperature - if this goes on long enough, the evaporator (A-coil, inside coil) can get ice on it, which really blocks the air flow. 

If it is past the lowest number on the thermostat the intention seems to be to turn it off. 

-Clean Dryer Exhaust Ductwork-Clean Refrigerator Coils-Clean Dishwasher-Clean Shower Heads-Inspect Sink & Toilet Fixtures for Leaks-Replace Air Filter-Re-Caulk Tub/Shower & Bathroom Floor-Flush Water Heater-Lubricate Garage Door Bearings-Replace Batteries in Thermostat & Smoke Detectors-Inspect slab for signs of termites; trench ground with Termidor every 5 years

We have Nest Thermostats installed and some tenants like that when we show our units. 

., if they are extremely energy efficient.If higher quality property, consider installing nest thermostats to help with energy savings since tenants won't care if they aren't paying the billI'm sure there are many more but those are a great place to start and get the bulk of your savings. 

21 years ago I decided that I didn't want Property Management to a full-time job even though I was going to self-manage each property.Now I have 28 apts with 60 or so tenants in 8 multi-family buildings in Brooklyn, NYC.I use a LOT of technology including electronic rent collection, electronic locks, internet controlled Thermostats, WiFi Cameras, Cloud Based CRM, Electronic Signatures (DocuSign), automated expense payments, etc.

I was thinking things like maybe a Nest thermostat or Ring doorbell -- something that is a few hundred dollars but that most houses won't have and will give me an edge over the competition.  

We had what we think was a ghost or squatter who kept opening windows after they were closed, turn up and down the thermostat and put socks on the ceiling fan blades.

Or you can raise the rents and include the utilities but then there is no incentive for the tenants to be conservative with the thermostat.

I live in Texas and don't know anyone that sets their thermostat to 72.