Buy an ACCURATE city map from Librairie DSM, which should set you back around 45dh (£3). The one from the tourist office is free, but very poor. Or ask a taxi driver for the district you require - and always insist on the meter (tho' if they refuse to set it, you only have to pay the minimum fare of 7dh, no matter how far they drive).
Librairie DSM
219 Blvd. Mohammed V