Hopefully you system has been converted to R134. That would increase the amount of troubleshooting you can do before you require an AC tech. Check the following things. Start the car, turn on the AC with the fan speed set to 4, and set the temp dial to the coolest setting. Look through the kidney grills and ensure that the AC fan it working. Connect an AC pressure gauge to low pressure connection. AC pressure should be above 30 psi for the compressor to turn on. Make sure the AC compressor clutch is engaged and the front portion of the pulley is spinning. Now look at the AC receiver dryer. It's located behind the passenger headlights. Look at the inspection window on the receiver dryer for the flowing refrigerant. Excess bubbles usually means you have a low charge. If the charge is low, add 1or2 cans of freon. If the still does work, take it to a tech. You could have a bad pressure sensor, clogged lines or valve.
Big Boyz with Bad Toyz.