Too add to what has been posted, you need enough water to cover the possibility of getting lost for a while. Plus according to Ned Overend, a big cause of the broken bones there is the slickrock which is slick only when wet. It has such great traction dry that folks start climbing near vertical slopes only to stall out. Since many/most? are not proficient at balancing on a steep angle, they fall off and tumble back down that hard slickrock.

On the tires, I called a bike shop there before I left for Moab. They recommended downhill tires. I didn't go that far, but did go to extra wide front tires (2.35's) after the first few rides to better handle the powdery sand. Some great rides like Monitor and Merrimac have some deep sand to ride before getting to the expanses of awsome slickrock.

You gotta have a camera. I lugged my big SLR plus heavy lens and didn't regret it one bit.

Al