How far to setup depends on the terrain. If it is really thick, you can get pretty close, maybe as close as 50 yards or so. If it is more open, you may not want to try and get as close. In the area I hunt, the birds dont always roost in the same spots, especially in the spring time. I do have some general roost "areas" that I can often expect birds to roost but not always. The only way to know for sure would be to get out there the night before and see if you can find out where they are roosting.