Fossil Exhibit Trail and Cliff Shelf Nature Trail are must-dos, but even these popular trails are primitive, so don't expect to see bathrooms or any hiking surfaces other than packed dirt and gravel. Because the weather here can be so variable, rangers suggest that you be prepared for anything. Wear sunglasses, a hat, and long pants, and have rain gear available. It's illegal to interfere with park resources, which includes everything from rocks and fossils to plants and artifacts. Stay at least 100 yards away from wildlife. Because of the dry climate, open fires are never allowed. Tell friends, relatives, and the park rangers if you're going to embark on a multiday expedition. If you have a cell phone with you, assume that it won't get a signal in the park. But most important of all, be sure to bring your own water. Sources of water in the park are few and far between, and none of them are drinkable. All water in the park is contaminated by minerals and sediment, and park authorities warn that it's untreatable. If you're backpacking into the wilderness, bring at least a gallon of water per person per day. For day hikes, rangers suggest you drink at least a quart per person per hour.