There are some facility and org requirements depending on the various company's rack setups, but most of that's standard.

The main requirement is how much traffic you need to be doing with the peer before they give you a rack - Apple states 25Gbps; more mature programs like Netflix are 5Gbps. Sometimes that's negotiable and they'll hand them out for even smaller traffic amounts (I've heard less than 1Gbps for some of those listed, though won't mention which ones). Like most things in this area of networking, there's a lot of variability and personal contacts involved.