This Grand Canyon "Death March" was my second such trip and I made quite a few improvements over the first time.
1. I didn't bother hauling a camera with me because I knew I wouldn't use it anyway. A point-and-shoot camera doesn't weigh much, but you wouldn't know that when you're nearly forty-eight miles into the trip, you're racing against the clock and a thousand feet of climbing stand between you and the finish line. Every bit hurts. Also, I knew my friend would take pictures.
2. After you're a few hours into it, every rest stop should include taking off your shoes. And unless your feet are made of calluses, you should do a thorough job of taping your toes, heels and any other typical hot-spots. Experience will dictate this. Get it right before you start so that you don't have to make adjustments enroute.
3. Salt pills.
4. Spend twenty-four hours at camp for the sake of altitude acclimatization before starting. You probably won't notice the altitude at all ... until you're on your final stretch back up at which point your arms (via trekking poles) are probably doing more to carry you up the hill than your legs.
5. Take a dump before you start. You'll thank me later.
The end result of Death March II was 19 hours 57 minutes. Having beat my twenty hour goal (and nearly four hours faster than last year) I don't see any need to go back for a third round but I probably will anyway.