Are you talking about a Class A? If so you go down the hill one gear lower than you climbed it in? For a regular test I would try and keep the RPM's around 2k.
It depends on how steep the hill is and how heavy your vehicle is.
If you find that when going up the hill in second gear you are getting too many RPM's, then yes shift up to third. But generally you should keep in the lowest gear possible, without overrevving the engine, especially if you're driving a loaded van or other heavy car.
I know that dmv book says when going downhill shift into lover gear now I find it strange because what is car is automatic or if you are already driving at about 2000 rpms and shift down gear your engine be making even more rpms but book says downshift. Sorry not sure what the book says about up hill but I know when going uphill depending on hill you shift down to get the car up on the hill. Hope this helps