You've got a great idea for a book and you're raring to go. You're sure it will become a best-seller. You start to fantasize about the great jacket blurbs you're going to get, and whom you will thank in your Oscar acceptance speech for Best Adapted Screenplay (you resolve to remember to thank both the Academy and your significant other).
Easy there, Tiger.
Getting a book published is a monumental undertaking, one that can make getting through both law school and the bar exam seem like small potatoes. Until now, most of your professional accomplishments have been largely within your control; do X and Y will follow. In the publishing world, however, even doing everything exactly right is no guarantee of success. But there are a few things you can do to sabotage yourself faster than than you can say "seven-figure advance":
1. Write the whole book first. You've written a brilliant 350-page book about the history of law in America, or tort reform, or the best way to come out on top in your sexual harassment lawsuit. And now you're ready to find an agent. Oops. Nonfiction books are almost sold on the basis of a proposal - a submission that includes a detailed outline of what the book will cover, some sample material, and information about the likely market for the book. You don't write the whole book at the outset, as it's likely that your vision and slant will differ somewhat from your future publisher's. You'll waste a lot of work - and time - if you write the entire book before you've found someone who wants to buy it.
2. Don't write the whole book first. This seems to directly contradict #1, and it does. Novels, unlike non-fiction books, need to be completed before you try to sell them (unless you're an established writer; Stephen King could probably sell a novel on the basis of a few scribblings on a cocktail napkin). While non-fiction is all about content, fiction is much more about style, characters, and plot. An agent will need to be able to read the entire thing to make sure it hangs together the whole way through. Memoirs, which are fact-based but reliant on strong storytelling, straddle the line between fiction and non-fiction; you should have your memoir finished before trying to sell it, but you should also be prepared to draw up a formal proposal.
3. Submit your book or proposal directly to a publisher. Most publishers refuse to accept unagented submissions. You will first need to find an agent willing to represent you, who will then act on your behalf to find an appropriate publisher. The vast majority of unagented submissions wind up in what's known as the slush pile - which is about as promising as it sounds.
4. Be a big jerk. This should go without saying, but oddly enough, it often doesn't. Agents and publishers don't like working with arrogant, pushy, self-important people. And, unlike your firm's paralegals, they don't have to put up with it. Be polite, be professional, and check the worst personality stereotypes of our once-chosen profession at the door.