Hi Canis and welcome to DHC. Salt or brackish water for puddlers is not that big a deal. Mostly, you'll be hunting larger water, so you may want a few more decoys than you would on small ponds or lakes. As far as decoy species, stick with the species of birds you typically see. Here on Long Island, there is very little freshwater hunting for ducks. Fortunately, the birds don't seem to mind one bit. We hunt mostly two different ways, from an accessable shoreline or from a boat. When we walk in, we typically carry anywhere between 18 and 36 decoys. I usually carry the larger amount, the reason being that if I have them with me, I can put them out. If I don't, I'm out of luck.
As far as hunting, some serious scouting will pay big dividends. The trick is to be where the birds want to be. We've found that a falling tide is the best tide to hunt. And make sure you account for the tide's rise and drop in rigging your blocks. Up here, we can have a 6 to 8 foot swing, depending on the moon phase, so we're generally running 10 to 12 feet of anchor line. The other thing is the current speed. In areas were the tide runs quick, you need to pay attention to your anchor weight and or design. Muffin tin anchors about 4 to 6 ounces with copper loops work well here, but we've got some really fast currents.
Hope this helps some.
I feel slightly sorry for a man who has never patterned his gun, who has no idea how far his chosen load will retain killing penetration. But I'm extremely sorry for the ducks he shoots at beyond the killing range of his gun and load - Bob Brister