I found this article interesting. I am currently interviewing for the CBN and this guy appears to know what he's talking about because he's an insider. You can ask him questions too..

"To get a job in the Central Bank of Nigeria is no easy task. The Bank aims to recruit the best hands from across the country and abroad, therefore the process is very competitive. The recruitment process is one of the fairest and most rigorous anywhere in Nigeria. Again, there is no error-proof process in the world not even in the World Bank, but the process in CBN is one of the most transparent, merit-based processes you can find in Africa. First, you must have a good first degree (Second Class Upper or Lower). If you have 2nd class lower, your chances are low, but who knows, your CV might have some quality experience which the Bank may require and thus might compensate for the grade, but it depends on other applicants as well. There are 1st class and 2nd class upper candidates competing for the same post and they might have quality experience as well—so if you are in University now, work hard on your grades. It could make a difference, especially for an entry level job. (Read the rest of the article here)"
http://www.oluikpe.com