Carry more water than you think you'll need, more food too. Just in case... While I normally wear a Camelbak on my back, that just wasn't going to work for this trip. Why? Because I was carrying a daypack for my camera gear, and two packs wasn't going to work. I thought about slipping a bladder into my daypack, but somehow the thought of a potential leak onto my camera (electronics) didn't sound like a risk I was willing to take. Instead I picked up a CamelBak FlashFlo, a waist pack that holds a 45 oz. (1.3 L) bladder. I also carried water bottles in the side pockets of my day pack, and I left an extra stash of water in my car. I was only doing short hikes; for longer distances I will need to figure out a way to carry more water.
I have to admit that I was shocked to see other people heading out on foot with only a camera in their hands, no water. That's really not smart...Recognize that if you run into a problem, or have an accident, that you're going to need to wait for someone to find you, to realize that you need help. And that cell phone you're carrying that usually is reliable - well, there's no cell phone access here.
Plan ahead - or not! Be careful, and above all, enjoy your Death Valley adventure!