When speaking to Arabs most tourists will learn some formal Arabic to accomplish some common 'touristy' tasks such as getting a taxi, buying and trading and exchanging pleasantries.
Beyond that another form of Arabic is used which is quite informal and can vary from country to country. This part of the language will often include casual exchanges, some of which are considered quite crude by Western standards, so care must be made as to the appropriate setting in which to use them.
As an outsider speaking to Arabs in your daily dealings with traders, friends and the street man or woman there are certain social norms that need to be followed if you are going to avoid hostilities (and they can arise easily).
First and foremost of these is asking about an Arab's current state of being. When asking an Arab about how they are it is acceptable to ask specifically how they but questions about their family should be vague and brief.
Asking about an Arab's wife is considered taboo, regardless of an Arab's religious background. More often than not you'll recieve a quizzical look from both Muslims and Christians if you ask about their wives, daughters or anyone of the opposite sex. Another common mistake tourists make when chatting to Arabs is remaining motionless when speaking. This is particularly apparent during trade negotiations. Arabic is an extremely descriptive and evoctive language and as such when mouthing phrases during conversation a hand gesture is expected when trying to drive a point.
Simply standing motionless and telling a trader you think their price is exorbitant will often have no affect but a waving hand accompanied with a smile can diffuse any situation in the souk (markets) and create a more flexible bargaining position.
Similarly, saying you like something the way you would say it in an English household carries little effect but a smile and an upturned hand saying "mashallah" shows your appreciation than a mere, "excellent".
When talking to Arabs, be they male or female, appropriate eye contact is of paramount importance. Whereas we have always believed maintaining eye contact is a sign of confidence this does not carry so well in Arab cultures. Maintaining eye contact for long periods of time when talking to a female or the opposite case can send the wrong signals.
Lingering looks can also produce discomfort and awkwardness among your Arab hosts and friends. The golden rule is to maintain as much eye contact as needed to convey a point. As in most conversations, chatting to Arabs requires patience, tolerance and listening.
A unique trait when talking to Arabs is to ease into the subject rather than get to the point. It is considered the height of bad manners to attend a meeting or talk to an Arab friend and simply get to the point without exchanging pleasantries.
The difference between this accepted norm in other cultures, is that even after exchanging pleasantries, the subject should still be broached in a roundabout way without making it the focal point of the conversation.