If your table wobbles and you have ruled everything out and came up with either a short or long leg never fear it is correctable as well. If you have a leg that is shorter than the others take a thumbtack and push into the foot of the leg. There are also floor protectors that you can get to go on the bottom of the legs that can help you raise a short leg.
If you determine that one leg is a little longer then you will have to shorten it. Do not use a saw because you will not want to take off much of the leg at a time. Get a file, wood file if it is wood and metal file if it is metal, and turn the table upside down and gradually file off the bottom of the leg. Turn the table over and check for level. Repeat this process until you have no more wobble.