Book as soon as you can. Check with the national parks to see how far in advance you can book, then reserve when the rooms are up for grabs.
Take advantage of last-minute cancellations. Tour operators book rooms far in advance. If a tour doesn't fill, they must release the spare rooms 30 days before the tour's start.
Stay at lodges farther from a park's main attractions. At the Grand Canyon, for example, many visitors first try to book at room at the historic hotel immediately on the South Rim, whereas the motel-style lodge 1/4-mile away (and connected to the South Rim by free shuttle bus) often has availability.
Just show up. It's a bold move, but travelers who arrive at a lodge looking for a room for that night might be able to nab no-show rooms. They're generally released around 4 or 6 p.m.
Visit during the summer's "shoulder seasons." Early June and September have fewer visitors, thus lodging is easier to come by.
Make a reservation, even if your plans aren't definite You can always cancel your room, with proper notice, if you don't go.
Pitch a tent. For a small fee, you can have your own slab of land for the night. Many campsites are first-come, first-served. Go to the site early to reserve your spot and have cash in hand; most don't accept credit cards.
