Stock up on the essentials before you go
Bare essential supplies include waterproof sunscreen, an extra pair of socks, a hat, a camelback-type water bladder, an extra water container and electrolyte capsules, which will help you replace everything you’re sweating out. You’ll also need easy-to-eat, protein-rich foods that are energy dense but don’t weigh too much, like trail mix, nutrition bars, and gels.  And obviously, you’ll need hiking boots, but if they’re new, be sure to break them in first—and that they allow enough room to loosen up the laces after the first few miles for comfort.

Prep your backpack the right way
Your water capacity should total at least 100 oz., and you can fill your reservoirs whenever you pass one of the fountains, which are located at Roaring Spring, Cottonwood, Phantom Ranch, Indian Garden, 3 Mile House and 1 1/2 Mile House. Bring your camera (that’s a no brainer) but leave your cell phone behind: the only coverage in the canyon is near the Phantom Ranch and even there it’s spotty at best. An extra quick-dry t-shirt is also a handy thing to pack. Once you sweat through your first shirt, you can swap it out for a dry one and hang the other by carabineer outside your pack. Swapping from wet to dry t-shirts over midday’s scorching hours will be an added comfort bonus.

Travel from North to South
You’ll be starting at the North Rim and crossing over to the South Rim. Why this direction? Quite simply, the North Rim is a ghost town, and lodging there is extremely limited. There are only three housing options within a 45-mile drive, so plan your trip several months in advance to make sure you’re guaranteed a room when you do arrive. The South Rim has a wider selection of lodging as well as plenty of spots for pizza and beer to reward yourself, so it makes for a  much more lively end to your long day. (Don’t forget—this isn’t an out-and-back hike, so you’ll have to shuttle a car from the start to the finish ahead of time.)