You can maybe detect a bad mount by observing how much shifter movement there is.  Maybe.  Or by watching the engine to see if it jumps a lot while someone clutches it in low gear with the emergency brake on.  But the surest way is to check it by direct observation.  A picture is worth a thousand words.  And here's the thousand words (more or less):

Jack up the right front side of the car and put it on a jack stand.  

Remove the right front wheel.  

Remove the front fender inner liner (instructions).

Notice the front mount on your right as you look into the wheel well.  Now you can slowly pry up on the front of the engine or under the oil pan, prying against the frame(*). If the mount is bad, you'll see the stud and center of the rubber mount lift right up out of the rest of the mount.  If good, the mount will stretch until the limit washer contacts the stop tab (although it's probably a bad idea to stretch the mount to its limit).  If the mount isn't separated, check the rubber for cracks as you stretch it through about half its travel.

If there's any oil on the mount, clean it thoroughly and find and correct the source of the leak; motor oil and various fluids will attack the rubber and cause it to deteriorate.

(*) A 1/2" breaker bar works great for this, and it makes a great lug nut wrench - lots of leverage - when fitted with a 19mm socket.