Fury has some great points and you'll find more than a few in the thread Aaron linked you to. I'll add this here as it's the best piece of advice I've learned from the guys over the years and credit to Joe for this tidbit: "Make him gobble because he wants you to call, not because you're calling." This requires some time afield to really grasp how it works in practice, but it is still intuitive enough to be useful from the start. It's easy to make a bird gobble (most days), but it's also very easy to over call when that's happening because let's face it, it's fun to hear them gobble. But calling too much can get you in trouble more often than not, so we have to be aware of the consequences of doing so. The only time I will call with the intent of making a bird gobble is at first light, or if I'm trying to locate him after several minutes (10+) of silence. The rest of the time, I try to let him dictate how much calling I do, especially if I know he's working towards me and knows where I am. Once I feel like he's "on the line", I'm going to wait for him to gobble, then I'm going to very lightly call to him with some clucks and purrs.
The only other time I call a lot is if I'm "fighting" a real hen. Then it's game on. It's fun, and good practice, to mimic her and try to cut her off. Doesn't seem to happen often, but I enjoy it when I do get the chance.
