Hotels and alternatives
Hotels in Agdz, 50 km from Ouarzazate (one good and inexpensive), Zagora, 120 km from Ouarzazate (handful of hotels, basic standards, OK prices), M'hmid, 160 km from Ouarzazate, and end of road (two very basic places, but camping is quite possible).
Restaurants and alternatives
Restaurants are found in all major stops along the route, but it can be twice as expensive as in Ouarzazate for the same quality.
Change money
There are banks in Ouarzazate and Zagora.
Transportation
Buses cover the whole distance, but note that taxis are less reliable here than in more populated areas elsewhere in Morocco.
Best is to join other travellers, and rent a car (unless you already got one) or a taxi. If you start early, and doing the whole trip in a day is quite feasible. Buses go, but not as often as you could wish, and leave hours before the sun rises. And beyond Zagora, connections are erratic.
Important
The sun is very strong, even in Winter, so take precautions. Bilharzia can be a problem in the river, and wading and swimming is not recommended. Floods have killed travellers before, so be careful if you camp out in spring.
Warning: The map of the Rough Guide is misleading: Just follow the only possible road south out of Zagora as far as it goes.