People travelling to Saudi Arabia need to take certain precautions to avoid last minute surprises.
You may be a first-time visitor to the kingdom or an expatriate who is returning after a vacation. In either case, the most important document is the Saudi visa stamped in your passport. Note that the dates mentioned in the visa refer to Hijri calendar and not the Gregorian calendar. You may use the tool provided in this page for converting from one to the other or can click on this link.
Note that once a visa is issued, it is mandatory for you to reach the kingdom within the specified date, otherwise the visa would lapse. This is applicable for both first timers as well as those who are on an exit/reentry visa. For those expatriates who were unable to return to the kingdom before the date mentioned, please click on this link to find the procedure for returning. Remember that when you reach the airport, even before you check in, the validity of the visa will first be verified by the airline staff. Since this would normally be in a separate queue, make sure to be in the airport quite early.
I would advise first-timers not to stuff items in your baggage unnecessarily. Almost everything is available in the kingdom, which is available elsewhere in the world. Bring in only those items which you consider absolutely necessary. Note that electric supply in Saudi Arabia is in two voltages, 220 volts and 110 volts , 60 Hertz frequency. Flat to round pin adaptors and vice versa are freely available in the market, so don't bother to bring those either.
If you are going to bring your personal medication, make sure that you have your doctor's prescription with you for the same, or it would simply be thrown out by the Customs upon landing. Alcohol and drugs are strictly banned items and users and peddlers face capital punishment. Some travellers from South Asia, bring poppy seeds ('khas khas'). Although this is quite commonly used in food items in that region, please note that it is banned in the kingdom. Although a well-known fact, I would like to emphasize upon non-Muslims not to bring in any religious material like books, idols, pictures, crucifixes, etc.
Do not at any cost offer to take the luggage of your unknown fellow passengers while checking in. These are difficult days, and who knows what the other guy has stuffed his baggage with!
I would advise you to bring plenty of passport size photographs (about 20 would be adequate, to begin with). You would have to fill in plenty of forms, particularly in the first few months after arrival and these photographs would come in handy. Atleast you needn't have to immediately run to the studio to have yourself photographed.
Do bring some cash in US dollars to see you through the first month, until you get your first salary. Money can be easily converted in Saudi riyals in any of the exchange centers in the kingdom. You may like to bring in your personal toiletry like soap, shampoo, etc., to see you through until you get your first salary. Food is relatively cheap , but you cannot say the same about accommodation. Temperatures reach extreme during summer and winter, so do come prepared with your personal clothing.
Working in Saudi Arabia is both a challenge as well as interesting, if you are well-prepared mentally. Hope the above tips were useful.