Excellent web site with instructions on how to braid:http://www.dreamweaverbraiding.com/index.htm
Click on "Braiding Instructions".
For practice, I made a "head" out of posterboard. I took a smallish (7 inches by 10 inches or so) rectangle of posterboard and rounded off two of the corners so it made a sort up upside down 'U'. Then I took a hole punch and punched holes all around the edge of the U (but not along the straight bottom edge). Then I took some old yarn and tied lengths of yarn to each of the holes around the edge.
This "head" was light and moved too easily, so I would hold it with a foot against our coffee table while I sat on the couch and practiced braiding. And sometimes, I'd have dh hold it while I practiced.
Something to keep in mind is that your skills and your daughter's patience will both grow. You can start off doing a couple of simple braids. As you get more confident, and as your daughter is more able to sit still, you can try French braids, Dutch braids, lots and lots of little braids, cornrows, etc.
Something that really helped convince my daughter to sit still and be patient while I braided was pointing out that if her hair was braided well, it would have fewer tangles (easier comb-out the next time), and often we didn't have to do ANYTHING to her hair for several days (even up to a week, depending on the style). She soon became quite willing to make that deal - sitting still until I got it done, then not having to mess with it for days.
ETA: DD is not biracial, but I thought I'd give input to this thread, since I taught myself to braid dd's hair using that website and the "head" I made. I hope my post comes in handy.