Tipping in Morocco: There is no "rule of thumb" per se regarding tipping in Morocco. Moroccans themselves might only leave a few dirhams on a 150 dirhams dinner bill. For tourists and visitors, 10% is more common for meals. In taxis, just round up to the nearest 5 dirhams, e.g. if the taxi meter says 17, pay 20. For someone who carries your bags to your room or from your hotel to a taxi, 10 dirhams would be appropriate, unless your bags are extremely cumbersome, or the distance is longer than a couple minutes walk.
The real question for many visitors is "what do I tip someone who has guided me to a place in the medina?" This happens all the time as the medinas can be confusing and the minute you stop to consult a map or look vaguely lost, someone will appear at your elbow to help you fnd the way. Many times, the de facto guide will be a child. If this is the case, 5-10 dirhams is perfectly acceptable if the child leads you to your destination. For an adult, 10-20 is appropriate depending on the distance covered. If the "guide" stays with you (at your request) for more than just a few minutes or takes you to multiple sites, then any where from 30- 50 dirhams would be a good tip. Keep in mind that an official guide for the medinas charge about 120-150 dirhams for a half-day tour (but of course, they will make a commission off anything you buy, so they have another source of income).
Occasionally, an unofficial "guide" will latch onto you even if you know where you're headed and then try to demand payment for his services. Obviously, you are under no obligation to pay anything. Several times I've had guides follow me through the medina trying to take me to the tanneries or wherever else, and despite my assurances in Arabic that I live here and know where I'm going, they will tag along behind me and then demand 20 dirhams for "helping" me arrive at my destination.
And what about beggars? Zakat, or the giving of alms, is one of the five pillars of Islam and is akin to the tithe system in the Catholic church. Many Moroccans will give coins to beggars as giving alms brings "baraka" or blessings from God. 1-5 dirhams is a common "donation". If you are not inclined to give (and thats OK too), you can say "Allah yasahel" (may God improve your situation) - or if that phrase escapes you, a smile will suffice. Peristent begging is not acceptable, and once you have refused, if the requests continue, it is OK to ignore them and move on.
Etiquette: The most important thing to remember is that Morocco is a Muslim country, so the local norms and customs should be respected. In practice, this translates into dressing modestly (see the Inside page for Female Travellers), avoiding public dislpays of affection (hand-holding is OK in more touristed places like Marrakech, but kissing - even little pecks - is a no-no), and avoiding public consumption of alcohol and public inebriation.
Taking photos of Moroccans going about their daily business is fine IF you ask for permission first. How would you feel if a Moroccan tourist to your country wandered into your office bulding, walked up to your desk, pointed a camera at you and snapped a photo and then walked off without a word?
Learning even a few phrases of Moroccan Arabic will win smiles and praise from you local hosts.
Moroccan men and women greet one another with kisses on the cheeks. The better you know someone, the more kisses you get. A Moroccan man would generally not kiss a woman he is greeting (whereas, he would kiss her husband), but might offer her his hand (if she is veiled or completely unknown to him, a simple nod of the head would be appropriate). You will see Moroccan men holding hands as they walk, but it is rare to see a man and wife doing the same. When greeting someone or responding to someone's asking "how are you?", placing your right hand over your heart as you reply is a gesture of sincerity and friendship.