Location, location, location!!!
...but your spread is important too. You need to make sure that you leave a reasonably large open area for the ducks to land. They don't like flying over other ducks to do so either. There are old proven setups like the "J" Pattern or the "C" Pattern where the back of the "C" or bottom hook of the "J" would be into the wind. Like airplanes, ducks always prefer to land INTO the wind so whenever possible, set up with your back to the wind and your dekes out in front oriented to allow for an upwind landing that should be right out in front of you, say at 20-25 yards.
As for river current, I have never hunted a river so I don't know if that's an issue. Maybe someone else can respond to that subject.
Btw....you MUST know our resident "Tater?"