First off, CONGRATULATIONS! That's awesome that you are adopting, and an AA child at that, seeing as they are often the least desired on the hierarchy of adoption. I am AA, and have a few friends who are white with adopted black/biracial children, so I have witnessed the challenges as well as understanding from my own perspective. I have a few what I would consider major points to understand:
1. Don't approach it as if the world is colorblind. your child is a part of your family but there is an obvious difference that should be respected. The world is not colorblind, and it generally causes the child to be blindsided when they are out of their "community" or family culture.
2. Have people in their lives who are also AA. To me that is so important b/c I have seen firsthand the importance of it. Understand there are questions you won't be able to answer from experience and that it just really helps, (and doesn't take away from your place as her mother/family) to have someone who they can relate to.
3. Try to expose them to and have in their life diversity of all kinds. (that's not just good for them it's good for you too.)
4. Do learn how to manage their hair, especially if you are adopting a girl. This sounds trivial but I could fill a book about my experiences (and those of the children) who's hair I braid and style for them. I have been in one child's life for 9 years and some of the stories I could tell you about her and her hair and the compelex relationship around it would fill up pages.
5. Support groups. It would be nice to find a group with similar families so you as a family can be supported and share.
I am an educator, who focuses on anti-bias work. This is a subject I have spent a bit of time on, as well as working with people who are in this exact situation. I can give you a book list, I just need some time to compile it for you. Feel free to email me if you would like more information. GOOD LUCK!!!