Check your thermostat
Check that the thermostat is in cool mode and set point is below room temperature
Make sure your filter is clean
1 inch filters should be changed frequently, media filters are to be changed according to manufactures specs
Filters are usually located inside the unit or in a ceiling grill
Check outdoor disconnect box
Make sure the power is on to your AC unit
Disconnects are located within 6 feet of the AC unit
Check all circuit breakers
Check that all circuit breakers are in the on position
Circuit breaker panels are usualy located in the basement or garage, though sometimes can be in other locations
Units that are located in attic
Check to see if there is any standing water in pan located under the unit
If so, remove the water for temporary AC and call for service
Units that are located in basement
Check to see that the condensate pump is plugged into a working outlet
If the outlet is a GFI make sure it is not tripped
Does your AC work?
If the previous steps did not resolve your cooling issues, Call for service