Well first, check to make sure your system was converted over from R-12 to R-134a (a sticker should be on the inside of hood detailing when it was convert see pic), if not your going to have to go to a mechanic and get the system recharged with R-12 (only certified mechanics can still by R-12 or Freon as it'* also called). Thats if nothing else is wrong. Although, I have heard that R134a will never be as ice cold as R12.
this car car website has good ac tips about A/C that can save you money. It helped me recharge my refrigerant. A/C may seem scary because if you mess up you can damage your car but with some online research and following directions on the ac kit or can, you can do a basic recharge of cooling. Anything else needs to be done by an expert.