No billion-dollar law firm could keep churning without having a few whales in the mix. And most Big Law firms have more than a few—the kind of clients with an enterprise so expansive that their need for outside counsel seems limitless. Due to their sheer size and voracious appetite for legal services, these clients are key to law firm growth, especially at the upper reaches of the Am Law 100.

Some firms have institutional client relationships that stretch back decades or even a full century, but those are few and far between. And in the years since they were formed, the process for landing these revenue-driving clients and maintaining them has changed enormously.