1. Not realizing you're in a Muslim country: Dress modestly (even if other tourists don't) and don't expect to be served alcohol in most restaurants. Businesses usually close on Fridays instead of Sundays. During Ramadan, you'll have fewer dining options.
2. Accept official prices: Morocco is the land of haggling. Merchants assume that their customers will negotiate prices when shopping at the markets.
3. Let your guard down: Moroccans are very friendly and welcoming, but don't be fooled; they also have families to feed, and many take advantage of tourists for this purpose. Stay alert and don't trust strangers who offer you tours, ask for directions, or inquire about your hotel. Try to connect with the local culture, but don't be naive.
4. Taking photos without permission: This is similar to point number 3. Many people will ask you for money in exchange for taking the photo. Make sure everything is clear before taking it.
5. Entering mosques: They are beautiful, but unfortunately, non-Muslims are not allowed inside. It's more a matter of respect than a written law or rule, so don't assume that just because there isn't a specific prohibition, you can enter without any problem.
6. Avoid independent travel: If it's an organized tour with a tour operator, there's no problem. But if you're a traveler who prefers to go it alone and book transportation, hotels, etc., according to your own criteria, don't let the chaos of Morocco intimidate you. Many visitors go directly to travel agencies because they're afraid of traveling around Africa on their own. Don't worry, Morocco is safe for foreigners, the people are very hospitable, and as long as you respect point number 3, you'll certainly have no problems.
Morocco is a beautiful and unique country with much to offer its visitors. Do a little research beforehand and you're sure to enjoy your visit.