I generally shoot ducks the same way Ragnarok says he does geese.
Keep decoys tight, allow openings within spread and on edge of spread for landing area for birds.
Try for shots as birds flair when committing to land.
Always amazes my duck hunting buddies to see me connect on a bird with a longbow. They never seem to remember the misses, but never fail to tell stories about the ones I connect on.
They all use shotguns. Funny how I sometimes shoot as many birds as they do, with nowhere near the number of shots. Semi-autos; what a waste of shells.
The big thing is, if your hunting among gun hunters be sure they are willing to allow you a chance at the birds before they begin blasting away!
I hunt with a bunch of understanding guys that appreciate my limiting the chances of a kill. In respect of that they will allow me 1st chance at the bird if I call the shot.
In return I don't rag them about using shotguns!