Appropriate Attire -- Although wholeheartedly Muslim and conservative by nature, Moroccans are also understanding of, and have been exposed to, Western culture. Unfortunately, many Westerners take this tolerance to the extreme, and dress as if they were back home. Travelers will be treated with undoubtedly higher respect by all Moroccans if dressed conservatively. For men it's worth looking around and seeing the type of dress generally worn by all Moroccan men: collared shirt or T-shirt covering the shoulders, long pants or jeans, and sandals or shoes. Running shorts, sleeveless shirts, and beachwear are only worn when playing sports or at the beach, and if worn at other times are almost tantamount to wearing only your underwear. For women, dressing conservatively can range from loose, long pants, shoulder-covering short-sleeve shirts, and shoes or sandals to a full-length Moroccan robe, called a jellabah. This rule of thumb covers both day and night, although is a bit more relaxed should you be visiting one of the country's finer restaurants or highbrow nightclubs, generally found in the more cosmopolitan cities of Casablanca and Marrakech. Some of these establishments are decidedly more European than Moroccan, and the dress of the clientele often reflects this. I would still, however, recommend "classy" over "revealing."
Greetings -- Moroccans are more formal in social situations than most Westerners. Queries about one's marital status and children are considered polite, and greetings should always include queries as to the health and well-being of one's family. Always greet with your right hand, as your left is traditionally considered unclean. Kissing cheeks is practiced between members of the same sex -- especially if they are friends -- but should not be performed between opposite sexes unless each is well known to the other. When entering someone's home, it's considered polite to remove your shoes, especially before entering the living/dining area. If your host doesn't require such politeness, he or she will quickly inform you.
Gestures -- Using your index finger to motion a person to approach you is considered impolite. Moroccans -- as with most non-Western cultures -- beckon someone by placing the palm downward and sweeping the hand toward themselves.
Avoiding Offense -- In Morocco, taboo conversation subjects include the royal family, the political situation in the Western Sahara and Algeria, and drugs. It's also wise to be prudent when talking about Islam and Al'lah (God). Although non-Muslims are not expected to fast during Ramadan, it's considered polite to eat, drink, and smoke indoors, or at least away from the public eye. At any time of the year, but especially during Ramadan, show respect in both dress and demeanor if you are near a mosque. Photographing a mosque is usually acceptable, so long as you're not too close or appear to be photographing the interior. You may be invited to come closer, but it's best to wait for this. Photographing border checkpoints, military, police, or airport installations is strictly forbidden.
Eating & Drinking -- In Islamic (and Arabic) cultures, the left hand is considered unclean, as this is the hand with which a person performs sanitary tasks. Moroccans, therefore, rarely eat with their left hand, perhaps only using it to drink from or maybe to pass bread. If you are eating from a communal tagine, eat with your right hand only. The respectful procedure when offered food is to politely decline and, if offered again, to accept a small portion. Reciprocating the offer is also considered polite, and will afford respect. To decline an offer of food, simply pat your stomach and shake your head, followed by "La, shukrran" (No, thank you).
Punctuality -- Punctuality is not one of the trademarks of Moroccans. Tasks are often achieved in "Moroccan time," which can be anything from a half-hour late for personal appointments to even arriving the next day. The exception to this rule is the country's guides -- especially the faux guides and hustlers -- who will be waiting long before any agreed time.
Hammams -- Traditionally, Moroccan women used to bathe nude, but nowadays this isn't always the case, with many younger women (and most travelers) electing to go topless but wear underwear or bikini bottoms. This will not cause offense; those who choose to also wear a bra or bikini top may do so, but local women will wonder why the visitor doesn't, like them, bare all. Men, both Moroccan and Western, bathe in shorts. It's not necessary to shower beforehand.
The Global Etiquette Guide to Africa and the Middle East (John Wiley & Sons, Inc.; 2002), written by cross-cultural expert Dean Foster, has some handy information for both business and leisure travelers on general cultural issues between Arabs and Westerners, and includes some specific advice regarding Morocco.