Queen Consolidated, Wayne Enterprises, LexCorp, and Ferris are all important companies in the DCUniverse and they should be used to create a sense of a shared world. It wouldn't have to be a heavy handed affair either, it could simply be a matter of hiding Easter eggs everywhere or quickly slipping lines of dialogue in. Things as simple as a delivery box or passing truck one show labeled "Queen Consolidated" or a cell phone that is maybe by "Wayne Enterprises" or a television station displaying "WLEX" would help the world building endeavour explained in the previous point and would actually make viewers want more, building a genuine desire for the crossover. Additionally, making mentions of famous people - either the heads of these companies or otherwise - would also establish that sense of a larger universe existing. Arrow has already proven itself capable of utilizing the larger DCU to fill its world, the other shows need to start dropping names quickly. The larger the world feels, the more believable a crossover event will be.
Brandon grew from the awkwardness of his youth into the awkwardness of his adulthood. He is the author of the Eat Your Serial Press title "Ten Years Gone: Pomp and Circumstance" and is a contributor on Maglomaniac, Polite on Society, and What Culture.