If the car still has the original mounts they are more than likely shot.
The proper way of checking is to measure mount height. If you don't have the specs, the best thing is to do a visual check. The obvious is to look around for cracks. Get a mirror if needed (especially driver's side) and look around the top for any signs of cracking. Check for any oil leaks around or under mount. They always leave a trace usually a white, yellow, or rust color. You can also try lifting engine by placing a piece of wood at the mount arm and checking if the mount separates.
Don't forget to check rear transmission mount. Check for separation by using a pry bar.