Never have a picture of a well-adjusted African on the cover of your book, or in it, unless that African has won the Nobel Prize. An AK-47, prominent ribs, naked breasts: use these. If you must include an African, make sure you get one in Masai or Zulu or Dogon dress.
In your text, treat Africa as if it were one country. It is hot and dusty with rolling grasslands and huge herds of animals and tall, thin people who are starving. Or it is hot and steamy with very short people who eat primates. Don’t get bogged down with precise descriptions. Africa is big: fifty-four countries, 900 million people who are too busy starving and dying and warring and emigrating to read your book. The continent is full of deserts, jungles, highlands, savannahs and many other things, but your reader doesn’t care about all that, so keep your descriptions romantic and evocative and unparticular... Your African characters may include naked warriors, loyal servants, diviners and seers, ancient wise men living in hermitic splendour. Or corrupt politicians, inept polygamous travel-guides, and prostitutes you have slept with.
Wainaina has a new book out that I'm hoping to read (after I recover from textbook purchases for the semester) and he is the founding editor Kwami?, a Kenyan literary magazine.