Buy primarily Bills and Cans -'Reds, Cans and Bills will readily decoy to those.
Get big decoys. Life size decoys are not big enough to show up in open water over distance. One guy I hunt with converted some Herters 82 goose floaters to Can decoys...deadly.
Believe it or not, we would run a couple lines of super mag black duck decoys on the outside edges - the black shows up better than you'd expect and draws birds. Brown/Hen decoys are wasted...drake cans/bb's and black ducks would make a killer diver spread.
Golden Eyes are the exception, they much prefer to decoy to their own kind, and will skirt a bb/can spread. If you want to kill them consistently, you'll need GE decoys.
Bufflehead will decoy to anything, but if you want to target them throw out 6-7 Bufflehead decoys exactly where you want to take your shots...they're magic.
If possible, get some motion in spread. Flags have killed more divers and sea ducks than I can even count in our spreads...I've seen 200 bird flocks of bb's turn in unison on a flag. Again, GE's are the exception - they hate flags and spinners and you can flare off a committed bird with a single wave.
Try to give you some idea how big I like decoys to be...raided my buddies photobucket account, I'm terrible at taking and keeping pics.
Converted Herters goose floater.
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