While the validity is noted in months, these are not Western months but lunar months, and you need to use the Islamic calendar to figure out the length: a three-month visa issued on "29/02/22" (22 Safar 1429, 1 March 2008) is valid until 29/05/22 (22 Jumada al-Awwal 1429, 28 May 2008), not until 1 June 2008! Depending on visa type, the validity can start from the date of issue or the date of first entry, and multiple-entry visas may also have restrictions regarding how many days at a time are allowed (usually 28 days per visit) and/or how many days total are allowed during the validity period. This all results in fantastic confusion, and it's not uncommon to get different answers from an embassy, from your employer and from Immigration!
Saudi Arabia has very strict rules for what may be imported: alcoholic beverages, pork, non-Islamic religious materials and pornography (very widely defined) are all prohibited. Computers, VCR tapes and DVDs have all been seized from time to time for inspection by the authorities. If you are unsure if the movie you watch or the video game you play is deemed un-Islamic, it probably be best not to bring them with you to the kingdom. In general, though, inspections aren't quite as thorough as they used to be and while bags are still x-rayed, minute searches are the exception rather than the rule.
aw and morality
The really important rules to beware of are enshrined in written Saudi law, with criminals subject to the full strength of the infamous Saudi penal system. In addition to obvious crimes like murder (punishable by beheading) and theft (amputation of the hand for repeat offenders), acts considered severe crimes include adultery, homosexuality and possession of alcohol or drugs.
In practice, though, most visitors will be primarily concerned with the code of morality, involving things like women not covering up properly, not observing prayer or (during Ramadan) fasting times, etc. These rules are enforced by the infamous muttawa (pl. mutawain), the zealous volunteers of the religious police formally known as the Committee for the Propagation of Virtue and the Prevention of Vice. Confusingly, the exact rules and their enforcement vary greatly both with time and from region to region, with the Nejd region around Riyadh being the most strict, the Eastern Province being the least strict, and the Hejaz around Jeddah being somewhere in the middle. However, 99% of the time, encounters with the muttawa (especially for non-Muslims) simply result in verbal warnings. The muttawa do have the power to detain those suspected of un-Islamic conduct, but — in theory — must hand them over to the police before interrogation, and neither can they apply judicial punishments like whipping without a trial. Reports of abuse and even deaths in muttawa custody are still depressingly common.
ex segregation
No women at the hotel gym
No women at the hotel gym
Many (perhaps most) areas of life in Saudi Arabia are segregated by sex to ensure that unrelated men and women have no possibility of "mingling" (khulwa, a punishable crime). Under the rules of segregation, all people are divided into three groups:
Families. The basic unit of Saudi life, families consist of women accompanied by their mahrams (legal male guardians) — father, brother, husband, uncle, nephew — and children.
Single men (bachelors). Men not accompanied by their families. Banned from most shopping malls and even some supermarkets from 4 pm onwards, this is by far the most restricted group Despite common use of the word "bachelor", it is irrelevant whether the man is married or not; a husband will dine in the bachelor section at lunch when alone and in the family section at dinner when with his wife. It is against the law to be accompanied anywhere by a woman who is not your wife or a family member. Religious police pay particular attention to interracial couples.
Single women. Women not accompanied by their families. Most of the facilities for families will admit single women, but they are rarely allowed in the men's section and are subject to uncomfortable stares when they are. It is against the law to be accompanied anywhere by a man who is not your husband or a family member (except a hired driver or a taxi driver). The punishment will be worse for the man than for the woman. While the man is forced to sign a written oath not to repeat the offense and may be subject to lashing or prison, women are generally "returned" to their families, with a male family member signing on her behalf. The cultural value placed on "modesty" and "honor" makes the religious police reluctant to openly "out" an offending female and will try to sweep the problem under the carpet, unless in more "egregious" cases.
Typical examples of segregation include:
Establishment Segregation
Banks Separate branches for men and women, but when a women's section is not available at a branch, women are allowed in the male branch.
Coffeeshops Mostly men only, although a few have family sections.
Hotels Single women no longer require written permission to be allowed to check in, provided they have their own ID cards. Gyms, pools and spa are generally restricted to men only, but some female facilities are available.
Museums Separate opening hours for families and men ("families" typically include single women).
Restaurants Separate sections for families and men. The vast majority will allow single women into the family section.
Shopping malls Allow all visitors, but often with evenings and weekends reserved for families and single women only.
Shops Usually allow all visitors.
Women
Women, be they local or foreign, are all required to wear an abaya, a long and loose black robe. While a headscarf is optional for non-Saudi females (particularly in Jeddah and Dammam), one should at least be brought along in order to avoid possible harassment from the religious police or to be used as a means of deflecting attention from potentially aggravating men.
Saudi law prohibits women from mingling with unrelated men. Some family restaurants will go further and will not (knowingly) allow a married couple to dine together with a single man. Women may not drive cars, although as of 2008 there are — not for the first time — rumblings that this may soon change. In theory, women may not even be driven by unrelated people (e.g. taxi drivers), although this is widely ignored and rarely enforced.
A woman may travel alone. They may also stay alone in hotels, although hotels may require written permission on check-in unless the woman holds an official form of ID.
While all this legally applies to foreign women as well, in practice foreign women are not restrained by their families in the way that Saudi women are, and can have considerable leeway if they choose to take it. For example, a foreign woman and her boyfriend (or even male coworker) can simply claim to be husband and wife, and thus mingle freely — although, if caught doing so, they could sometimes be subject to a short stay in jail.
A single woman accosted by the police or the muttawa and requested to come with them does not have to (and, for their own safety, should not) go with them alone: you have the right to call your mahram and have them arrive, and you should use it. However, you may be required to surrender your ID, and you may not leave until the police/muttawa allow you to.
[edit] Other
Photography is probably the easiest way for a visitor to inadvertently get into trouble. Do not take pictures of any government-related building (ministries, airports, military facilities etc) or any building that could possibly be one, or you risk being hauled off to jail for espionage. As Saudis place a high value on privacy, do not photograph any Saudi men without permission and do not even point your camera in the general direction of women, period. Even government publications avoid pictures of people and often resort to mosaicing out faces if they have to use one!
Playing music in public is also prohibited (though this does not include playing music at a picnic in the desert for example). However, personal music players and listening to music in private is fine, and there are plenty of music shops in the country's shopping malls if you don't mind permanent marker over Britney's hemline on the cover. It is not uncommon to hear young Saudis blasting the latest hip-hop music in their vehicles, at least when the muttawa are not around.
Religious items for religions other than Islam, including Bibles, crucifixes and any religious literature, are technically forbidden, although these days items for personal use are generally ignored. However, anything that hints of proselytism is treated very harshly, and the muttawa often bust illicit church assemblies and the like. Public observance of religions other than Islam is technically a crime in Saudi Arabia.
The flag of Saudi Arabia bears the Islamic declaration of faith, and desecration or any other inappropriate use of the flag is considered insulting. Public criticism of the King, the royal family or Saudi Arabia's government in general is not tolerated.
Saudi Arabia travel guide - Wikitravel