EDIT: Please note the following items:
The Mission Requirements for claiming the Grand or Second Place Prize include the following:
Landing – A team must land its craft on the surface of the Moon after providing advance notice of its launch and intended landing site to XPRIZE.
Mobility – After landing, a team must move its craft a distance of at least five hundred meters below, on, or above the lunar surface along an interesting path in a deliberate manner. The distance can be a straight line or may be a series of waypoints approved by the Judging Panel.
As in some games of pool, you have to indicate your intended landing area ahead of time. Your actual landing site should be close, and allow for an acceptable course of travel for your rover. If you are driving a lunarized Sand Flea maybe the second part is relatively easy. Otherwise, you don't want to end up at the bottom of a hole or wedged in a crevasse.
As I've said here there's no GPS on the moon. I am presuming the Lunar X Prize landers will start from an established lunar orbit (where they can get their bearing and wait for a final "Go" from Earth). This gives them time to receive any of various potential beacon and telemetry signals from Earth, and data from their cameras (e.g. Earth, Moon, Sun, Stars...)
But once descent has started, I am not sure which of these are still helpful, during attitude, and especially propulsive maneuvers.
I don't want to know about any competitive secrets, or "special sauce" that that various teams are counting on, but from a general perspective, what navigational information is likely to be useful for these small, limited budget, limited development, limited previous experience lunar landing craft?
If the Moon were a smooth sphere with a painted pattern on it, a nice landing might be done with some nice cameras. But the Moon has substantial topography - would they need to be ready to do a "Neal Armstrong" and look around for what looks like a good place to land? Or could they use a "rover-friendly" region map and have precise enough navigational data to put themselves down within a few meters or tens of meters of an absolute spot?