The hunt begins as soon as you step foot out of the truck. In darkness you must have a proper route to get to your set up. If a bird watches you from 100 yds back in the bush walk the feild edge with a flashlight and set up your dekes, load your gun and get ready, he's probably not coming to feed in that feild. Be quiet, slip along, heck crawl if you have to. Get into your set up undetected. It is not a natural sound for a turkey to hear a limb break, a cough, sneeze etc. Some guys think because it's still dark and the turkeys are "asleep" they can get away with more.
I believe you said they gobble and have been seen in this feild at springtime so that's the biggest hurdle. They don't necessarily breed (or hens don't necessarily nest) where you see them at other times of year.
If they are call shy try nothing more than a flydown with your cap and/or awing. Maybe a couple purrs and clucks if you get a gobble from the flydown. Give a few yelps is fine but what kind of yelps? You need the right feeling for the moment. If you're going for the subtle, relaxed turkey sound (usually the best bet) then you don't want those couple yelps to sound excited. A few excited yelps and then you stop could hurt you. The gobbler hears this excited hen and then she shuts up. What gives? He might think something doesn't seem right. Pay attention to the feeling in your calls. You don't have to be a good caller to kill a turkey but you have to have emotion in your calls. After that listen to his emotion. It will help tell you what he is thinking and whether you should adapt your calls.
Is thier hens usually there? It could be that you aren't necessarily doing anything wrong but good ole mother nature is beating you. A live hen will win. If this is the case sometimes it is patience that gets left in the truck. If he walks off and goes with a group of hens he will possibly breed, be shut out, or lose the hen (like if she goes to nest). In any case it might be 3-4 hours later and he decides to head back to the feild to see if that morning bird (you!) is still hangin around. Hunt until you can't hunt anymore. If your state is noon then try staying put until noon. 11:45 am could be the turning point for finally tagging one of those birds
