Most dove spreads are built to be seen from a mile out. That part is easy — motion and contrast do it. The part people think less about is the last forty yards, where a bird stops reading the field as a whole and starts reading individual decoys.
Put the spinner where the bird looks last
Run the spinner on the upwind edge of the spread rather than in the middle. Birds come in downwind and finish into it, so the spinner should be what they are looking at as they commit — not something they pass over on the way in.
More than one reads differently
One spinner reads as one bird. Three spinners running at slightly different heights read as birds working a field. Stagger the stake heights and do not line them up in a row.
Clip decoys do more than people think
Twenty clip-on decoys along a fence line or a dead limb cost almost nothing and give the spread a resting population. Motion says come here; static birds say it is calm here. Most good spreads have both.
Then walk out and look back
Walk forty yards out and look at your own spread the way a bird would. That is the only honest way to judge it — and it is exactly the exercise that led to Wing Skins.