Like JW said i like to get in tight and mimick a one of the older hens. i got into a hen fight yesterday morning with a flock of hens for a gobbler but they won and pulled him to the other side of the 10 acre field.
they may not be goin to the field in the morning but they could be coming out in the heat of the afternoon. scout in the afternoon and see how they enter it and how they leave it. pretty much the same as deer. this way you know the general direction they are coming from and how they enter the roost site.
other than that just wait it out till the hens go on nest. then they will be all over.