Nigeria is a largely cashless country and most businesses (even in the open market) have POS systems to make transactions possible. Never ever carry a lot of cash around or worse, flash it.
There are numerous photo ops located throughout Lagos. While street photography has become a thing, make sure to ask before taking pictures of people or businesses.
Airport hotels are really great with fantastic ambiance and food. However, hotels in Lagos are quite distant from the important landmarks and beaches, and it can be expensive travelling those place from the hotels.
Staying on the right side of the law is relatively easy in Nigeria, and it’s best to stay that way because bribing a police officer is illegal and comes with heavy fines or even a jail term.
Those going someplace should have the correct address, take an Uber ride, or use Google Maps. A lot of locals do not know where a lot of places are in Lagos and instead of admitting to not knowing the location, they will misdirect visitors. In extreme cases, ask for directions at taxi ranks or from Okada Riders, but do not ask a random stranger on the street for directions.
Tourists should go clubbing in the company of others. There are qualified tour guides who can provide company or directions to groups of people hanging out together at specific times.
Nigerian Customs is extremely efficient and they have their methods of monitoring tourist visas. Follow travel plans and leave the country on or before the visa expiration date. If there’s a need for an extension of stay, there are provisions in place.
Lagos is an exciting city with several landmarks (beaches, museums, etc), but the worst mistake to make is to go to popular spots during the weekend because Lagos is also the most populous city in Nigeria. Weekends are downtime for most people and the only period they have to visit those spots, so they are usually crowded. It is also advisable to have a private and experienced tour guide—particularly true for first-time visitors—even if it’s just for consultations.