Prepare yourself physically before attempting the hike to Half Dome. The trail to Half Dome is 8.2 miles from Yosemite Valley one way, making it a 16.4-mile round trip. Train by walking outdoors or on a treadmill. If training with a treadmill, be sure to adjust the incline to simulate walking uphill--much of the trail is steep. Also, train while wearing a backpack to get used to carrying around the extra weight of your supplies.
Gather the supplies you will need on the trail. Items to consider include a backpack (a day pack-sized bag should be sufficient), water, water filter and food. Snacks such as trail mix, granola bars, fruit and pretzels are great things to have to eat while on the trail. Energy bars can also provide the necessary kick to ensure you have enough strength to make it to the top of Half Dome and back. You should also pack emergency supplies, such as a first-aid kit, a whistle, a flashlight and flint in case something goes wrong during your hike. Be sure to pack some bandages and another pair of socks in case you find yourself afflicted with blisters--these are especially common with those who do not properly break in their hiking boots before the trip.
Consider the clothing that you will wear during your work in addition to the backcountry supplies. Zip-off pants are a good idea, since it may be colder in the morning when you start off your hike and much warmer by the time you approach the shoulder of Half Dome. Long-sleeved shirts can help prevent sunburn; the same is true of a hat. Thick socks and hiking boots should complete your hiking ensemble. If you're worried about your footing during the hike, plan to bring along some trekking poles to give you added traction. The last portion of the hike involves hauling yourself up 400 feet of cable (at a 45-degree angle) up the side of Half Dome.
Plan to arrive in Yosemite a day or two before you plan to hike to Half Dome. Once in the park, you may want to drive up to Tuolumne Meadows to aid in your acclimation to the park's high elevation.
Choose your route. There are two main routes to Half Dome. The most popular route is via the John Muir trail from Yosemite Valley. This route is about 16.4 miles in total length. A second option is to start from Glacier Point (you will need someone to drive you to Glacier Point, or a partner with a car at Yosemite Valley so you can retrieve your car later). This route takes the Panorama Trail to Nevada Fall, where the trail meets up with the John Muir trail. Although this route is slightly longer, it has the benefit of not having the initial steep ascent required by taking the John Muir trail up to Nevada Fall.
Start your hike early in the morning. This will ensure that you arrive on top of Half Dome with plenty of time to return to the valley floor before nightfall. Getting an early start also gives you a leg up on all the other Half Dome hikers. In general, the Half Dome hike takes about 10 to 12 hours, depending on your fitness.
Plan breaks during your hike. Breaks give your muscles a chance to rest and gives you time to adequately drink water and eat some food to keep your energy up.
Take account of the weather when you arrive at the shoulder of Half Dome. If there are any thunderheads in the sky, or it looks in the least like it might thunderstorm, heed the warnings and do not proceed. Lightning strikes are fairly common on top of Half Dome, and it is a danger that should not be taken lightly.
Use caution while on the cable route, perhaps the hardest part of the trail. The cables are up typically from the third weekend of May to Columbus Day in October. Unless you are a highly skilled climber, do not undertake this ascent when the cables are not up. Take your time when going up the cable route, and be sure to have a good grip on the cables. Stay within the confines of the cables, and do not walk outside them. Deaths from falling off the cables, while not common, are still possible.
Congratulate yourself and enjoy the view once atop Half Dome. Take time to walk around the periphery of the dome and take a look at what Yosemite looks like without Half Dome in the view.
Keep your eye on your watch, and give yourself adequate time to return to the trailhead. Although most of the trail is downhill, you will be tired, and steep descents can lead to knee pain, causing you to travel even more slowly.
Take the time to get a massage the day following your epic hike if your funds allow for it. Doing so can help alleviate muscle pain and, after such a long hike, you deserve a little rest and relaxation.
