Before you start working on a proposal for a non-fiction book, it's important to know what else is out there on the topic and what is being sold in bookstores. To do this properly, you have to pry yourself out of your desk chair, put on some real clothes, and head out to a bookstore. Looking on Amazon or other online sites won't help you because they list everything- even books they don't stock themselves. Bookstores, on the other hand, only stock what's selling as their margins become thinner. They can't afford to warehouse dozens of copies of each book anymore.
While you can (and should) go check out your local indie stores, their quirky natures and stocking preferences aren't going to give you a solid foundation on what people are looking for in your topic. You need to head out to your local Barnes & Noble or Borders (or, if you're in Canada, Chapters/Indigo).
Spend some time there browsing the aisles and checking out the end caps and featured tables. Take a notebook with you and jot down what the "hot" books in your category cover and, more importantly, what they're missing. See who your competition is and who publishes them. Watch customers browse your category and see if you can pick out what makes them choose one book from the shelf over another. Don't be afraid to strike up a conversation and ask them why they chose that particular book. Was it the title? The colors? The brand name?
All of this valuable information can be put to use in your proposal and in your book. It will help you forge your unique angle on your topic and provide information that readers have a hard time finding elsewhere. It also helps you pitch your book idea to publishers, showing that you have an understanding of the market and what is missing that you will provide.
At the very least, it gets you out of your own self-absorbed and lonely world of writing and makes you rub elbows with the most important people in your life-- readers.
