swampcollie gives some good advice. In addition I think they have the ability to make a lower sounding gobble when are on the move and searching for hens.

Hilly country can be a good advantage. I like to get above the calling bird and set where the gobbler will appear at the crest of the hill in easy gun range say 30 yards. He will probably only stick his head up first to look around, but you need to see the beard. He may pull his head back down allowing you to adjust you sighting location, if not hopefully he will pass behind some trees within the next 10 yards so you can make your final sight adjustment.

I think you will find it is not a good idea to peak over the hill to look for him if you even think he is close. A turkeys eyes miss very little especially movement and there could be other turkeys in the group which are much closer to you than the gobbler calling. One PUTT and they are all gone.