Camo the pit and adjacent area as well as possible. you can't over conceal. Use colors and materials indigenous to area so it looks natural. Keep as much of pit top covered while you're hunting and only have caller looking at birds to minimize movement.
Don't get too greedy trying to get them in super tight. Often the second or third pass is the best you'll get...watch the birds closely and change your spread and opening each day according to the wind direction.
Ya can't kill em sleeping in the bed!