Things I have learned, always always always get as close as physically possible before making the first peep to a bird.
Set up where I can see about 40 yards, and try not be able to see "a long way".
Be natural with your calling, very very rarely do hens stand around cutting and yelping at the top of their lungs. They usually do most of their communication with almost inaudible yelps and very low lucks. In other words calling softer was a huge thing I learned.
The most important thing other then getting close, is to be patient. Turkeys are in no freaking hurry usually, I have killed probably 30-40 birds in the past 10 years that years ago I wouldn't have, simply by putting my calls down and just waiting for 30 extra minutes after a bird went silent.