Short answer: Keep writing! Do your homework, and don't give up!
I didn't know anything about publishing until shortly before I started GIFTS. JenEndyB gave me some info and recommended resources. I was discouraged at first, as I investigated, because it seemed like it was really tough to get a foot in the door with a publisher. But with non-fiction books, the #1 rule is to write about something that people will want to learn about, in a fresh way. I knew the DS community would love to read a book like GIFTS, and that society at large desperately needed such a resource. I knew DS had never been written about in this way--the book would be unique.
Woodbine wasn't interested when I first pitched the idea. They said they already had a book of personal experiences written by moms of kids with disabilities (can't remember the title now). I urged them to reconsider, and thankfully they did. They're enjoying unprecedented success with GIFTS.
So, if you have an idea that you think would make a good book, start by doing your homework. There are many guides available about the publishing industry and its different aspects, such as literary agents, query letters, book proposals, etc. Don't get intimidated--thousands of new books are published each year, by people just like you. If you believe that your book would be eagerly read by many people, do the research needed to hone your approach so that you can convince a publisher that you have a dynamite idea.
Above all, don't let the challenges of publishing keep you from writing! There are many important reasons to write--publishing is just one of them. You might need to write for you, or for your family. Your writing might be needed by people who will find it even if you never get a publishing deal (for example, on a website, or a self-published booklet or book). Also, the industry is constantly changing--if you don't find a toehold now, you might later on. KEEP WRITING!
Kathryn Lynard Soper
Mother of Thomas (DS) 10/2005
Sam - 2003
Matt - 2001
Christine - 1999
Andrew - 1997
Ben - 1994
Elizabeth - 1993
Author of The Year My Son and I Were Born: A Story of Down Syndrome, Motherhood, and Self-Discovery
Editor of GIFTS and GIFTS 2