Been there a number of times, here's a brief outline. As you don't specify VFR/IFR, I am assuming VFR:
1) you will have to fly VFR routes. Suggest you program these into your GPS, as the VRPs are in many cases impossible to find/see w/o local knowledge.
2) check NOTAMS, they have a lot of D/R areas, plan around the activity time (a particularly pesky one lies right across your path from Spain to Fes - active, IIRC Mon-Fri).
3) you are expected to call Casablanca at the FIR boundary. Unless you are 7000 ft or higher, you won't be able to..
call the nearest airport (Tanger or Tetouan) for relay
4) you will be expected to make position reports along your route in the format XYZ at VVV, expecting ZZZ (i.e. next VRP) at xx.xx(Z). ATC is ok, but they do it in three languages (English/French/Arabic), which sometimes, well, you get the drift....
5) overflight of ANY ciity in Morocco is prohibited
6) if you speak ANY French, use it ! Not on the radio, but on the ground, it makes a world of a difference.
7) Bakshish (i.e. a little tip) to the guy at the AIS is welcome in the South, frowned upon in the North. Use common sense. Generaly staff at the airports are very nice and friendly and, if asked nicely, will sometimes go out of their way to help you. As an aside, you usually have to go through the same checks (both passport and security) as the SLF. Find an official, tell him you are aircrew (and show your license) and you will be escorted past the huddling masses
8) The Atlas mountains are a serious mountain range; do NOT underestimate them !! You will also be flying in a hot n'high situation, make sure you can actuallly get across (if indeed you plan to do so).
9) In the South, check 100LL avail. Errashidia for example does normally NOT have it. You also pay slightly less for fuel when departing internationally.
In general it's a great place to fly. Fab scenery, nice people and quite different. I personally prefer the South (other side of the Atlas) where it
really starts to feel like Africa, but anywhere/s interesting.
Enjoy!
HTH