First step is to check if you have a leak. The way to do that is to remove the vacuum line from the C/C vacuum pump, which is on the left fender right behind the windshield washer jug. You'll definitely have to remove the battery, and probably the windshield washier jug as well, unless you can reach it without removing the jug. Plug the end of that vacuum line with something, a golf tee works great in my experience.
Next, remove the plastic trim underneath the dashboard.
Push the brake pedal down by hand just until resistance is felt (this opens up the vent valve that is activated by the bake pedal), and then push the throttle control element diaphragm in (black round thing about 3 inches across, right about the gas pedal). Release the brake pedal, and then the throttle control diaphragm. If the end of the vacuum line (by the pump) is sealed completely, the diaphragm shouldn't move. If it doesn't, then there's no vacuum leak and you probably have an electrical problem. If you know you have a good seal at the end of the vacuum line, and the diaphragm moves, you have a leak somewhere. The trick is then to actually find the leak.
There are a number of possible places to have a leak. The first thing to check is the hoses. Start under the hood, the hose that is attached to the vacuum pump is the most likely one to sustain damage. Look for cracks, you may have to squeeze the hose to expose them. Then check the vacuum lines under the dashboard.
If the hoses are good, test the brake vent valve. It's a little blue unit about 2" long and 1/2" wide right above the brake pedal. Take the vacuum line off it and plug it (make sure the other plug is still there), and do the test again, except this time you'll have to use the clutch pedal instead of the brake pedal to open up the vent valve in order to push the throttle control diaphragm.
If the diaphragm doesn't move, then the problem probably lies with the vent valve on the brake pedal. If it still moves, then check the clutch vent valve.
Reattach the vacuum line to the brake valve, and remove the vacuum line on the clutch valve and plug it. The clutch valve should look the same as the brake valve. Do the test again, use the brake pedal to open up the system so you can push the diaphragm again. Release the brake, then the diaphragm, and if the diaphragm doesn't move, then the problem probably lies with the clutch valve.
If neither valve leaks and you still have a leak somewhere, it's probably with the throttle control element.
Hope that made sense.