I'll be watching for an answer to your question. I've been wondering the same thing.
I don't think indies (or even big 6) have any control over that. It shows up once you hit the top 100 for whatever category. Now, how Amazon sorts you into said categories - I think that's done with much waving of hands and some woo-woo.Amazon Best Sellers Rank: #107 Paid in Kindle Store (See Top 100 Paid in Kindle Store)
#1 in Kindle Store > Kindle eBooks > Fiction > Fantasy > Contemporary
#1 in Books > Science Fiction & Fantasy > Fantasy > Contemporary
#8 in Books > Literature & Fiction > Women's Fiction > Contemporary Women