If you've ever played a wind instrument before, calling at them with a Mallard call should be pretty easy to do if you spend some quality time on Youtube researching vids about the kinds of calls they make and what they sound like, and WHAT those calls MEAN in their world. And commiting that to memory. And then do the practice while in the car with the windows up thing. There's basically, as I understand it, just 3 (maybe 4) sounds for you to do. The kind of social calling they'd do amongst all the other ducks who arenearby with them in the water... Then.. a more urgent and excited version of that, which you might think of as them seeing some other ducks passing by overhead and they're trying to be like "Oh Hey! Hey Friend! Come on down here and socialize with Me! I noticed you flying by and that got me excited to be social with you!" Or at least that's how I'm choosing to interpret the difference I hear in the calls. And then.... lastly.. they have this sort of more subdued and quite staccato type of sound they do when they are happy and feeding on something, which can be used to add more realism and possible appeal to the other ducks hunger.
For me in the very open desert-y landscape out at Wister in the Salton Sea, a leafy suit of appropriate color such as the bushes out there, and similar mesh facemask has worked great!
You just make your sit location nice and low and within or in-between some of the bushes/brush right up to the muds edge, trying to remain in the shadow so you're not cooking out there in the heat of that place.
Other than that just don't be dumb and do like you'd do in any hunting situation and keep your movements to a minimum. Especially when they have eyes on you approaching overhead. In other words, I'd say try to avoid raising that duck call to your mouth if they are incoming and would be able to easily see those movements. But if you already had your arm up to your mouth because maybe you were calling at them while they were up high and off to one side flying by... then by all means just keep your arm in that position if they then have successfully turned to now fly incoming to you. Minimize your fingering movements while cupping the call and also have a similar camo pattern of liner gloves on, to blend in with that leafy suits colors and you'll do well at remaining unseen, without needing to drag in a buncha isht to the spot and build up a ground blind from external materials you brought in with you. If you had a dog that retrieves I could see how that route might be necessary though so the dog could remain hidden until needed.
If you're serious about it, I'd definitely invest in some decoys. I don't have a lot of experience with ducks, Only 3 seasons under my belt so far, and even I was able to several times convince ones flying over to turn around in a circle and come back around to where I was setup... only problem was other hunters in the next section over... the ducks would obviously be able to see far from up there in the air... they had decoys and I didn't... so that particular day it was upsetting me to no end because multiple times I'd get them to come back and them being up in the air like that... they'd see these others guys spread and I guess they just assumed it must have come from over there instead? And I got to watch them pop several ducks that should have been mine. That stung to have that happen while I was getting eaten alive by Mosquitos out at Wister, CA. So the next day I ordered some decoys and those fully coated Texas rig cables with like, I wanna say 4oz? or maybe 6oz? Cupped weights on em that dig into the sand so the wind wouldn't move the decoys into deeper water that I wouldn't be able to get into with waders.
I say that because the other gentleman I went there with the first time... one of his dekes ended up getting moved over in the water by the wind into an area where he could not retrieve it anymore to take it back out because he encountered some kind of trench in the mud, presumably from the small amount of water current in this one section created by the breeze which sometimes runs thru, perhaps carrying the silt to elsewhere, I'd imagine.
Only thing I'd say is, to my ear... the Wooden calls sound more life-like to me. Umm... only other thing I can think of is... if where you are experiences cold/freezing kind of conditions, you might want to research on vids and forums for people mentioning that this call or that call has problems with the reed freezing-up and perhaps becoming inoperable on you while you're out there. But I'd imagine most of the manufacturers now likely make calls where this has a lower chance of happening than before. I also remember reading if you are in those kinds of weather it's good to store the call when not immediately needed back against your body on your person so it can be kept warm so the reed won't freeze.
DEFINITELY bring Mosquito spray AND a ThermaCell. if they are needed where you are going, and you don't have them, you may have a horrible experience. (And even WITH them, you can still get bit-up a bit.
I have a friend who is a practicing doctor in a few different roles, one of them ER duties sometimes and when she saw the pics I posted of the back of my Tricep, and on my back, for example... she didn't believe it was Mosquito bites and literally thought I'd come down with Shingles (since I'm early 50's now), because it was that bad looking!
It's my understanding that some folks like the more raspy sound of an acrylic/plastic type of call for the purpose of it reaching out further trying to make high up and farther off ducks potentially hear it and turn back around. I just noticed the audible difference between the sound of my calling with the prior plastic one I had, and then I'd be hearing around me what I first thought for a split-second might have actually been a real duck in another section over on that waterfowl reserve, but then I later figured was somebody else using a call that just plain sounded better. So I asked around and also researched it... and that difference in tone, I found out, was likely because those other people were using a wooden call instead.
So then I ordered a um... (checks his Amazon orders.)
And to my ear, it sounds noticeably more lifelike.