What academics need to know about writing for a trade audience

While the books I represent generally are for a trade audience, and are available through Barnes & Noble, Amazon and independent bookstores, a number of my authors are academicians, and also have written for more academic audiences. Very often, that is how their book career began. Today, more categories, such as neuroscience, education, learning, botany, history, and more, are crossing over from academic/textbook to trade, as those authors are able to reframe their material or generate a new spin for an alternate receptive audience.