You got some great advice so far but I'll add a couple things.
I'll repeat the advice to get a good whistler call. After the season has been open a while it'll outperform the quacker. Quackers are good for getting their attention when they're way out there but you need to back off when the birds are heading your way. When they look serious about working your decoys, stop calling so they don't pinpoint your location which will not be where your decoys are. After they pass overhead, you can resume calling as they're going away. When they swing back, shut up. It's not how much you call, it's how well you call, your technique.
Decoys: White is very visible, you want it brilliant so ducks can pick it up way out there. Repainting parts of new or old decoys is needed. A drake Mallard should be much lighter on the back than many of them come new out of the box. As the season progresses it's more important to have decoys that look like live, active ducks, than huge numbers. 5 or 6 will get the job done if they have actual duck movement. I built a pulley system to get real swimmers. Calling wasn't necessary with that setup once I had the ducks attention. They wouldn't even circle. For every hen mallard, have two drakes because that's usually how it is in the wild. Drakes are more visible as well. Those spinning wing decoys work for uneducated ducks but there aren't a lot of uneducated ducks after the season has been open a couple of weeks. Ducks want open water to land in. Don't have you blind on top of your decoys if you're using a lot of decoys. If something isn't working, birds flaring, not committing, something is wrong, fix it. Could be something not associated with your decoy setup like foreign objects in the water or on shore. Camo face and hands and keep movement to a minimum. Don't look up at the birds as they pass overhead. You know they're there, don't need to look at them till it's time to shoot. A lot of times it's location, ducks just don't want to be where you're set up. Moving just a short distance can make a huge difference. Read the birds.
Blind: Natural materials. Learn how to hide in the open. Ducks figure out there's danger in heavy cover or big boxy blinds that stick our like a sore thumb. Be picky about your camo gear, a lot of it is too dark.
Another trick. If there's a lot of water, throw out some decoys that look like decoys where you don't want the birds to land. They'll home in on you setup if it looks real.