I've hunted the Platte River here in Nebraska for many years. Hilltop's recommendations are spot-on! Find slack water.
If you are packing in your decoys, don't be afraid of water keel. Don't ride the water as nice, but much lighter.
Some swear at the spinning wing decoys, others swear-by them. Check local laws to make sure you are not in violation.
We have had good luck using 18-24 duck decoys split in to two groups. Leave the opening right in front of your blind / hide. Ducks don't mind approach / landing over the top of Canada decoys...but I've found Canadas don't like approaching over duck decoys (not sure if you have Canadas in the area).
I would for sure mix in some Canada decoys to your spread, even if just two floaters. Bigger bodies, white tails = highly visible. Consider getting some RealGeese silhouettes. I made longer stakes and put them right in the river. Made it look like the water was shallow enough for a Canada to stand in...ducks loved it!
Some guys love to blow on their duck call, and some are quite good. Others should leave the call in the truck. You really have to play it by ear and see what the ducks are responding to that day. I've spent days on the river where we didn't even blow the call...and the ducks would pile right in. Other days nothing we did seemed to work.
And don't be afraid to hunt late in to the season...if you have, or can make open water, that's a great thing! Years ago we hunted a public marsh in south central Nebraska in December. Ice was thick enough for us to stand on it. We managed to break open an area probably 20 years around, threw a few decoys in, placed the rest on the ice. Killed a limit in no time. Open water sucked them right in!
Good luck. Post some pictures if you can. But don't give away your honey-hole. Daubs