I thought I might bring up some of my experiences shooting the sand dunes in Death Valley National Park. I am by no means an expert (I have only shot two dunes) but I have a couple of tips that I haven’t seen mentioned elsewhere.
There are five main sand dunes in Death Valley; Eureka Dunes, Mesquite Dunes, Ibex Dunes, Panamint Dunes and Hidden Dunes. Eureka is the highest, Mesquite the busiest and the others rarely visited. I don’t really think Panamint or Ibex are all that difficult to get to but they don't get a lot of foot traffic, so if you want to go to a pristine dune field those are you're best bets.
For better or worse, I think Mesquite is the most photogenic, due to the more golden color and the longer length they cover, giving the impression they go on forever. Mesquite has one big drawback and that’s the footprints. The tallest parts will always have footprints, as everyone wants to get to the top. The areas that require at least a 1-2 mile hike from the parking lot though should have few to no footprints.
As with all landscape photography, but especially dune photography, you’re going to have to get to the dunes at the very least one hour before sunrise/sunset. I think there are three distinctive periods during sunset/sunrise to shot. I’ll use sunrise as an example; pre-sunrise glow (civil twilight), sun at the horizon (dawn) and finally golden hour.
In the pre-sunrise glow period you generally either want to be high up so you can get the most of the glow, which emanates from the horizon line, or far back from the dunes taking a wider shot.
You’ll generally be looking at strong silhouettes being cast due to the large dynamitic range, so make sure you bracket, even if you have a D810/A7R. It is worth mentioning that if you do climb up high on the dunes at this time, you’ll leave footprints for any pictures after sunrise (this doesn't have to be a bad thing as you can use them to create leading lines).
Next, you have the sunrise, with the sun actually at the horizon and visible. Rather than looking for side-lighting shadows here I would recommend using the sun in the composition. Sun-stars are the obvious choice but there’s also using the dunes to create leading lines towards the sun. Again, the dynamic range here is going to be a lot (even more than civil twilight).
If you haven’t started climbing the sand dunes yet, you’re in luck as the path leading up to the peaks of the sand dunes are perfect spots for sun stars. Make sure you get low if you’re close to the peak and be ready to focus stack if you get really low.
Finally, there’s golden hour. Really you have more like an hour and half after sunrise to look for shadow interplay in the dunes. The sun should be low, so you should be able to find areas that have both strong shadows and fully illuminated parts.
While a lot of people will tell you that photographing sand dunes is difficult, I would disagree. You have to move around a lot and think about your next shot while say you’re camera is firing off bracketed shots, but you’re come away with a lot of good pictures, rather than just the usual one or two. Make sure you plan ahead; check for cloud cover, how high the clouds are likely to be, the wind speed and of course the direction the sun will set or rise. Oh yeah, one more thing, make sure have some fun, if photographing this way isn’t you’re idea of fun do whatever gives you a blast!