When you go to restaurants in Morocco and when you pay at the end, it may happen that the cashier deliberately won't give you back correct change.
Say, for example, that you have to pay 40 Dirham. You hand over 100, and of course are supposed to get 60 back.
Instead you will get 50 back, and they hope that, you being a stupid tourist, you won't notice because you are unfamiliar with the currency.
They wait a little whether you might notice. If you stare at the money and count, the suddenly they are like "Oh, yes, and of course ten more Dirham, here you are". They've kept the 10 Dirham coin in their hand just in case you notice. Had you not noticed, they would have kept it. Clever!
So familiarize yourself with the money and count your change!
You can hardly go into the Fez medina without having tens of people offer you to guide you around in there. You will probably see as many people when you're already in the middle of the medina, who want to show you the way out against money.
Admittedly, it can be nice once or so to have a proper guide guide you around to see the sights (which you might not find by yourself). But you will always find out by yourself, somehow. The fun thing about the old city is to just disappear into it and walk around and around, although you don't know where you are. That way I always discovered new places. I also in the end always reappeared at a place again from where I could remember the way out. There are many exits and entrances. Although the medina really is like a maze and very large, you'll always make it out again by yourself.
Even after having been in Fez for month, I was still being offered to be guided around - or out!
Unique Suggestions: Have the guide experience once. They might go with you to carpet sellers with whom they probably have a deal. If it interests you and you want to buy a carpet, fine. Otherwise, keep declining. It's probably not the cheapest way to buy carpets anyway.
Fun Alternatives: Roam the medina by yourself. Let yourself by surprised.
When you contract a local guide to see the zoco or anywhere you must get an agreement of the price BEFORE HAVING THE SERVICE DONE. But get sure if the price is the total or per person, because they are very intelligent and are used to treat with tourist...
Fun Alternatives: There are not may alternatives, if you want you can contract a "legal guide", but they will be more expensive. But if you want to see the zoco you need on guide, so you choose.
Haggling is wide spread so be careful specially when they see you are a tourist the price jumps I bought some thing the guy asked 350 after haggling i got it for 90 only.