The most important thing to do is get a detailed topographical map before setting out on any overnight hike. These are available at many Yosemite stores, visitor centers, ranger stations, and the Wilderness Center in Yosemite Valley.
Permits & Fees -- All overnight backpacking stays require a wilderness permit, available by phone, by mail, or in the park. Permits can be reserved 2 days to 4 months in advance and cost $5 for each individual on the permit. Reservations are accepted, usually beginning in late winter. Call tel. 209/372-0740 or write to Wilderness Permits, P.O. Box 545, Yosemite National Park, CA 95389.
If advance planning isn't your style, first-come/first-served permits are available up to 24 hours before your trip. Permit stations are located at the Yosemite Valley Wilderness Center, Wawona Information Station, Big Oak Flat Information Station, Hetch Hetchy Entrance Station, and Tuolumne Meadows Information Station. (Many of these are open summer-only; Badger Pass is the lone winter-only permit station.) Permits for the popular trails, such as those leading to Half Dome, Little Yosemite Valley, and Cloud's Rest, go quickly. Call tel. 209/372-0200 for permit station locations and hours.
To get a permit, you must provide a name, address, telephone number, the number of people in your party, the method of travel (snowshoe, horse, foot), the number of horses or other pack animals if applicable, start and end dates, start and end trail heads, and principal destination. Include alternative dates and trail heads as well. Do not neglect getting a permit. You may hike for a week and never run into a ranger, but one is guaranteed to show up and ask to see your permit just as you are re-entering civilization.
Special Regulations & Etiquette -- Campfires are not allowed above 9,600 feet, and everything you take in must be packed out. Backpackers must take bear-proof canisters for storing food. They can be rented for $5 a trip at the Yosemite Valley Wilderness Center and at several other park locations.
