You can check the state of the condenser radiator. If that is obviously corroded or holed then there is no chance of the a/c working. The next step would be a re-gas, preferably using a dye, to find out if the seals are holding. If they aren't the dye should show where. If they are holding and the condenser is okay and it still isn't working the next stage would be to pressure test the compressor pump.