Lagos: many european crews stay at the Sheraton, so do we when we have to stay there. Bring cash. DO NOT USE CREDIT CARDS! Anywhere! Nigeria has the highest rate of credit card fraud. Do not leave the hotel for anything! The Sheraton has a very popular pool and tennis courts, there is not much else to do during the day. Food is outrageously expensive, but supposedly the owner has everything shipped in from outside the country. Three meals a day will set you back over a 100 bucks for basic stuff. A little fancier dinner add another 50.
Aids is all over.
For ground transportation call the hotel and see what they recommend. It does not mean you'll be secure, but maybe a bit safer than a taxi. I've heard horror stories about other cities in Nigeria where cops, cab drivers and hotel employees all participate in the same robbery gang.
Best advice: have your boss or customer buy a ticket on BA, Lufthansa, KLM, Air France, Alitalia or Virgin. Definately the safest and probably the cheapest option. You take a private jet in there and you're automatically a rich man who can provide for at least a big part of the population of Lagos.....