.
Africa is not by definition dangerous. There are some VERY dangerous places there, there are some others that are relatively safe. Nigeria is weird. There are Lagos and Port Harcourt that are very dangerous. In PH are a lot of kidnappings related to the oil business. Lagos is a 18 million people steaming pot where everything is possible. Abuja (the capital city) is supposed to be quite nice and relatively safe, just like Kano. If you take-off out of Lagos, fly west over Benin and 30 minutes later land in Accra, Ghana you enter a totally different world. Friendly people (who hate Nigerians), organized traffic, power that stays on, working traffic lights that are being obeyed, and even tourist tours. There are a few more countries in that corner that are not bad. On the east coast of Africa there are Ethiopia, Kenya, Tanzania, Uganda where you can move around without much trouble.
As a white guy you will always stand out and automatically are a have-a-lot while there are a lot of have-not's around. In other words, an easy target. So apply a bit of common sense about where you go and preferably go with another person.
In many places a cell phone is a very desirable thing, so don't wear it obviously, same goes for camera's and money (don't stick your wallet in your backpocket) and limit the amount of money you carry on you .
Also remember that simple things that we take for granted are not always available. Also human decency standards are different. It is quite common to see a grass field being used as a toilet by several people. Not like the US where public toilets are being removed and nobody knows where to go to do their "business". A field and grass leaves are sufficient. Not just in Africa, everywhere outside the developed "first world".
Most cities are very dusty. Lot of animal traffic. Go around a corner and find yourself surrounded by a couple of hunderd sheep or goats on their way to become dinner. Stray dogs and cats everywhere. Open air markets on the side of the road that bring traffic to a standstill. Remember the mid-eighties Mercedes 200/300 series cars, of which you still see one once in a while in the States? In Lagos there is a car rental place that rents them. You see like 20 of them lined up and each one is in immaculate condition. Just unbelievable given the state of the rest of the vehicles on the road there.