Fez is much nicer than Marrakesh. Take a day to get lost and wander round the souk. Marrakesh at night is not all that great unless you are there on the right nights, it was fairly empty the first time we went, except for the food places and annoying women who attacked you with henna and then demanded money. Go out for the evening, find a bar and chat to the locals, had a great night in Fez doing that.
Eat lots, at some point you'll be ill and the weight falls off. Although the options are pretty much tagine or Cous cous unless there is something local.
Essoaira is nice.
The town at the "entrance" to the sahara is full of knobs in 4x4s.
Country side is very nice. Generally the further away from the tourist places we got the nicer the atmosphere was, less pushy more friendly. Some tourist places are touristy for a reason so are worth going to.
Don't buy a carpet and lots of things are over priced for tourists – don't buy things from shops that don't haggle as they were the worst.
Buy some yellow shoes.