Working in Nigeria can be a very positive experience. Nigerian organizations tend to operate like small families, taking in newcomers with open arms and avoiding the coolness and sterility that often characterize the Western professional work environment. For instance, don't even think about coming into the office in the morning without greeting each of your colleagues. Even if you don't, be sure that they will go out of their way to greet you and inquire about your well-being.
It is hard to make generalizations about a country with 140 million inhabitants, but some Nigerians have a work ethic that would put most Westerners to shame. An eight-hour day not including lunch seems to be the norm, though it's not uncommon for people to stay late into the night and even come in for a few hours on weekends. Depending on the organization, a foreigner may be able to avoid this, but one should be prepared to work beyond the standard 35-40 hr work week.
The notion of "African time" applies very much to the work environment in Nigeria. Meetings are regularly held later than scheduled and often take longer than necessary. Although Nigerians will unabashedly admit to their habitual tardiness, rarely does one see efforts to correct this behavior. The higher ones position, the later one may arrive at a meeting. On top of that, starting the meeting before the important people arrive is very rude--a common principle shared with many Western countries. One should note, however, that when dealing with foreign organizations, Nigerians will often make some efforts to correct this behavior, for some Nigerians are aware that their conception of punctuality is not shared by all.
Those who are used to the strict North American conception of political correctness at the office may be shocked by the more liberal inter-sexual relations in the Nigerian workplace. Mild sexual jokes are common in meetings and in the office in general, though usually good natured and harmless. A white person working in an all-Nigerian workplace should also be prepared to frequently be reminded of their skin tone, though never in a nasty way. This can become tiresome, but Nigerians are generally very friendly. They use the term "Oyibo" white man in Yoruba or "Bature" white man in Hausa as a form of affection.
The use of professional titles in written and verbal form is very common in Nigeria. Expect to address your boss as Sir, Doctor, Colonel, etc., and avoid using the first name of a superior unless given permission to do so. Being a foreigner, you will be forgiven for any faux pas, but it is always best to err on the side of caution and politeness.
The mobile phone cell phone is an essential tool for virtually all urban - and most rural - Nigerians. Because of the instability of local networks, many people have two or even three "handsets", each on a different network. Anyone doing business in the country for more than a few days should consider having a mobile phone.