The vast majority of flights to Nigeria arrive in Lagos, although there are also international airports in Abuja, Port Harcourt and Kano. Airports are well organised and have official porters, but plenty of touts outside.
Airports & Airlines
Departure tax is included in the price of a ticket.
The main border crossing is on the Lagos–Cotonou (Benin) highway. Expect requests for bribes. There's a good direct Cotonou–Lagos bus service run by Nigerian bus company ABC Transport. An alternative border crossing is further north at Kétou on the Benin side.
There are two main border crossings. The northern border post is at Bama, 2½ hours from Maiduguri, across to Banki in Cameroon. A remote alternative crossing is at Ngala (Nigeria), which is used mainly for transiting to Chad. Both are currently inaccessible due to political problems.
The southern border crossing is at Mfum (Nigeria), near Ikom. The road infrastructure collapses pretty much as soon as you cross to Ekok (Cameroon), making this border problematic during the rainy season, so consider taking the Calabar–Limbe ferry instead during the wettest months. However, at the time of writing the ferry was not functioning.
Although there are no official border crossings between the two countries, it's theoretically possible to make a quick transit across Cameroon. In Nigeria, the border crossing into Cameroon is at Ngala. On the Cameroon side ask for a laissez-passer to allow you to make the two-hour traverse to the Chad border point at Kousséri. However, political instability in Chad means this is currently inadvisable.
There is heavy presence of security and more scrutiny because of Boko Haram, as it is believed that they have operations in Niger.
Before the insurgency there were four main entry points into Niger. The busiest was the Sokoto route, which crosses at Ilela (Nigeria). Minibuses and bush taxis ran daily to the border, just past Ilela. Crossing to Birni N'Konni, you could get on a bus straight for Niamey. Travelling between Kano (Nigeria) and Zinder (Niger) was equally straightforward. The final option was between Katsina and Maradi.
From Niger, it was easiest to cross at Gaya. You'll had to hire a bush taxi to take you from the Nigerian side at Kamba on to Sokoto. Beware the potholes.
A ferry sails from Calabar to Limbe every Tuesday and Friday evening (N6000, five hours), returning on Monday and Thursday. It's an overnight trip in each direction. Your passport is collected on boarding and returned at immigration. Try to keep hold of your luggage – if it gets stowed in the hold, you'll be waiting hours to get it back. Note that there are safety issues with the ferry, and at the time of writing it wasn't functioning. Take local advice.