We did parts of it many times, when I was in the military. We crossed over into NV to the Nellis AFB Bomb Range. We didn't carry weapons, because it's mostly public land and didn't want to frighten people, just tan BDU bottoms, and white or tan long sleved T-shirts.
There is a large pool of drinkable water in DV, but you have to know where it is, and dig a small but deep hole to get to it, so like previously mentioned, carry water, and stash water ahead at different waypoints in your trips. Plastic jugs of water are cheap, so stash more than you'll need. If nothing else, you can use the leftover to "bathe" with. If you use a GPS, make sure you can use a map and compass, at some places, you can get very confused if your GPS goes blitz on you.
In the summer, we traveled mostly at night and holed up during the day, which BTW we did that a lot during desert training. On a moon lit night, you can see almost as well as you can in the day.
I suggest this, others may differ. Eat little or very lightly during the day, If you eat a big breakfast, or lunch, it will cause your body to use much more water in the digestive process. Eat your big meal an hour or two after sunset or later. If it were my first time I would do it during Winter/Early spring.
Wear proper clothing, a proper hat, and I'm assuming you'll be wearing suitable quality sunglasses. If you take them off as the sun starts setting, put them back on at least 30 -40 minutes before dark. This will allow your eyes to adjust to the dark, and keep you from suffering night blindness. It makes the transition from light to dark better and quicker.
Although some parts are fairly easy, some are really tough, so plan your trip accordingly, as to your physical conditioning, age, etc.
Also, make sure you have a Topo map. Dry creek beds, and other landmarks can change over time due to flash floods.
We had to do it in the summer, sometimes, and if you do, plan for accordingly. It can really take the wind out of your sails.
Although some people don't use them, It's a good idea to get a package or two of the powdered or tablet like electrolytes to add to your water. If you're going to stay on marked roads or trails, it's a little easier, but (especially in the summer) it can be a really hard go. I would suggest, unless you're very well versed in desert backpacking/hiking, that you do as much research as possible. It can be extremely rough at times, and people do die out there.
But with careful planning, it's very dooable, and has multiple types of desert terrain, so depending on your trip, it can be really enjoyable.
Here is a good
Link to Hiking Death Valley J.