Whatever the birds were doing when I scouted them. Calling is based more on how the birds are reacting. Remember natural is best. If everybody around is running two groups of decoys I'm going to do something different.
Everything from a J hook style, 2 groups, 3 groups, no real groups, a bunch of small groups, one big raft, or my personal favorite the W all have their place. Too many people get hung up doing the same thing IMO. Let the birds, the wind, and cover tell you.