First, check the cleanliness of your HVAC system's air filter which is typically located behind the glove compartment. If it's clean, or if you replace it, that should take care of the problem. While you're servicing that filter, take a look at the squirrel-cage fan blades. If they're filthy, they might need attention too.
I've read elsewhere that the A/C will work best with a clean filter and the blower fan on the second-to-highest setting. That gives time for the air to pass over or through the heat exchanger so it gets the coldest.
Also, it's recommended to use the "Recirculate" setting, rather than the fresh air intake setting. That way, you'll be recooling already cool air instead of trying to cool hot outside air.
