One of the most common mistakes in calling is calling too much!  It's kind of like rattling in a whitetail deer, less is more!  When a tom gobbles at you, be quiet.....he thinks you are a hen and knows where you are.  If he doesn't talk, then cluck and yelp (a little) in order to gain his attention but then shut up.  Wait and listen.  You might imitate a hen flying down by flapping your cap or a turkey wing.  Just don't over work the bird.