I'll mirror what Puma says. But you asked how you obtain an independent distributor, and this is more difficult. Distributors have sales forces that cover a wide territory. They have established relationships with genre buyers from all the indies, chain stores, and libraries. Everyone knows that competition is fierce, so distributors are predictably choosy about their clients. The lineup, or series, has to be marketable and the publisher has to have an established promotional machine. It's a buyer's market, and indie distributors have the luxury of being choosy.
First off, you'll need to fill out a financial statement and include your business plan. You'll include your lineup and sales history. If a distributor finds your company (or book series for the self-pubbed author) marketable, they'll charge anywhere from $5,000 to $20,000 to become a client.
Some distributors are better than others, and some I'd avoid at all costs - even though they have a big name. IPG is very good. And very expensive. I've heard many success stores of those who are with IPG and some heartbreaker stories. Always keep in mind that just because you've been signed on with any distributor, if you don't bring in the goods - meaning your books aren't selling - you more than likely will be dumped after a year or so.
The main thing to do when shopping for an independent distributor is to ask around. If you find someone you like, call their clients and talk to them.
It's the single key to being successful, so how does a publisher accomplish this? Who do they approach and what to do they show off?
It's not the single key to being successful. Distributors get the book in front of genre buyers, but they aren't miracle workers. First thing buyers ask is, "What are the publisher and author doing to promote this title? How are they creating demand?" If they aren't doing anything, it's going to be a hard sell. They look for an author's platform, and that's why you'll see IPG and most other good distributors are heavy handed with nonfiction and niche works. It's easier to sell.
Anyway, I hope this helps a bit. Happy birthday!