Decoying can be one of the most rewarding and frustrating hunting tactics you can use. I took the deer in my avatar using a Delta buck decoy, so I can honestly say I have had one work for me. That buck was the dominate buck and he was absolutely ticked off that there was another buck in his territory. He made a bee line straight for my decoy.
Other days I have wanted to throw the thing in the trash. The antlers Delta provides are a basket 6-point. Believe it or not it I have had several nice 8-pointers tuck and run from this thing. Your medium sized bucks just aren't looking for a fight. This year I am going to equip mine with shed fork antlers and see if this helps.
As far as set-up goes #1Predator has it right. You want to set the decoy up with a bucks approach in mind. Does will go nuts over a decoy. They will stomp and snort at one just trying to get it to move. They will keep their distance, but they will get as close as comfortable in order to get a better look. When you set one up you want it to be as visible as possible. A decoy only works if deer can see it. You don't want to set it up in an unnatural spot where it looks out of place, but you want to make sure it can be seen. In the open works best, but on the edge of brush might work well if that is where deer normally travel through.
Hope this helps. Good luck this year!