I very rarely use decoys. The setup has to be just right. I typically only use them when hunting the edge of a corn or bean field- and the decoy is in the field facing me but at a quartering view. A buck is going to approach the decoy and eventually come to the front side to face off with it - if they are even interested. So the idea is you want them to NOT be able to see you while you are drawing back or getting sighted up for your shot. I will tell you this, when buck that is a shooter comes in, get ready b/c if they start to "fight" with your decoy and knock it down... 9 times out of 10 they will run off and be GONE. You want to take your shot ASAP,,, hence the quartering facing you pose of the decoy.
...and on that day when my strength is failing, the end draws near and my times has come, still my soul will sing Your praise unending, ten thousand years and then forevermore!