Since the end of World War II, a significant number of people of African ancestry have emigrated to the U.S. from the Caribbean, where their ancestors were also slaves (primarily at the hands of the British, Dutch, and French). Once you have determined that your ancestors came from the Caribbean, you will need to trace Caribbean records back to their source of origin and then back to Africa. You will also need to be very familiar with the history of the slave trade into the Caribbean
Additional Resources:
Caribbean Genealogy
The information discussed in this article is just the tip of the iceberg of the vast scope of African American genealogy research. For a much greater expansion on the six steps discussed here, you should read Tony Burroughs' wonderful book, "Black Roots: A Beginner's Guide to Tracing the African-American Family Tree."