Attitudes and behaviour in the Kingdom of Saudi Arabia are as different from the Western way of doing things as almost anywhere in the world, so be prepared for a healthy measure of culture shock. This is a fundamentalist Islamic state, governed by the laws of Islam, which it's important to remember apply to visitors as well as locals. The possession of alcohol, pornography, narcotics and even pork could lead to arrest and imprisonment. More serious crimes attract even harsher punishment.
The segregation of the sexes must be taken equally seriously. This is a society where - with a few notable exceptions - men deal with the work side of life and women the home side. As a visiting businessman, you are unlikely to encounter Saudi women in either a business or a social context and a visiting businesswoman must be prepared to put current Western attitudes to gender issues completely on hold. It is still illegal, for example, for a woman to drive in the Kingdom. Nor may women travel alone. Any man who accompanies a woman in public should either be her husband or a close relative. Saudi women who wish to leave the country need written permission from a husband or father. Businesswomen must employ male agents to obtain the paperwork to start a business. And so on.
Dressing modestly is of course essential for both sexes. Women should always cover bare arms, legs, shoulders and head. Only face, hands and feet should be visible and clothes should tend towards the baggy and concealing. Tight trousers and trouser suits should be avoided. Men should not wear shorts that come above the knee.
Like other Arabs, Saudis take pride in their long-established traditions of hospitality and generosity. Your hosts will go to great lengths to make you feel welcome. If you are invited for a meal, you will not be expected to pay, though making a token offer is always acceptable.
A Saudi man will shake hands with every man present in a room, but never with a woman, unless she is a close relative, in which case he's more likely to kiss her. Visitors should follow suit and not expect cross-gender handshakes. Remember, you should always shake with the right hand, as the left is traditionally ‘unclean'.
People in general stand closer to each than they do in the West. A hand on the arm or shoulder may be used to emphasise a point. If things are going particularly well a Saudi man may even take another man's hand (though never a woman's). This is a sign of friendship and has absolutely no other connotation. In general, you should avoid pointing the soles of your feet at people, as this can be seen as offensive. The ‘thumbs up' gesture is also rude.
The standard greeting is Assalam alaikum (‘Peace be upon you') to which is replied Wa alaikum assalam (‘And upon you too be peace'). Visitors should wait for this reply before entering a room.
In conversation it's fine to be forthcoming though it's best to avoid talking about politics and religion. Try no to lose your temper as keeping ‘face' is a big consideration here.
Arab names follow a simple pattern. The given name is followed by bin or ibn (literally ‘from', but meaning ‘son of') followed by the given names of father and grandfather and then a family name preceded by al-, meaning ‘from the house of'. So Osman bin Sultan bin Ahmad al-Harithi means Osman son of Sultan grandson of Ahmad from the house of Harithi. Women, likewise, are defined by their male ancestors, separated by the connective bint or binti, meaning ‘daughter of'.
Titles such as Doctor, Professor (Ustadh) and Engineer (Mohandas) are always used. Shaikh (chief) should only be used with the first name. In all cases you address someone by their title and first name - Dr Osman. When you get on more familiar terms with a Saudi, you may use their kunya, whereby you refer to them as Abu (‘father of') followed by the name of their firstborn. So Abu Abdullah is a nice way to address your friend whose firstborn is called Abdullah.
Saudis generally entertain at home but are happy to accept a foreigner's invitation to a restaurant as part of Western custom. If eating with hands, the right must always be used, the left is unclean and should not be used even for offering a dish.