Heating or Cooling not working? Here's some things to check!
Check your breaker or fuse. Sometimes power flucuations can cause a unit to kick the breaker or blow the fuse. Be sure to check the breakers or fuses in your main panel as well as at the unit.
Check your filter. A dirty filter can reduce airflow, causing a gas furnace to cut out on high limit and can cause an air conditioner to freeze up. Remember most standard filters need replaced monthly so make sure you check this.
Check your thermostat. Make sure it is calling for either heating or cooling, that it is sit on the right mode. Some thermostats require batteries to operate so make sure the batteries are good on this type thermostat.
Make sure you have electric and gas if it is a gas unit.