Hi Dan! Sorry I got so busy and didn't respond to you yet, but I can help. I'm more than a little bit swamped through thursday, when I gotta go to a big workshop for my client, present my shite and make a speech, woo! (Only 30 minutes, tough. Remember the words of Winston Churchill!)
I've got your mobile number, are you out and about today, it being a red day? If you're around, I could call you maybe about 3:00 or so if that's cool.
In the "how much can you earn?" category, some simple maths will give you an idea. Basically, any book comp/design publisher expects to seel a *minimum* of 10,000 copies, which for them is a bad book, barely break-even. Ideally you'd sell in the range of 30,000 copies, which starts to make things worthwhile. If you get a contract, you get money two different ways, an up front "advance", and a "royalty" based on sales. If you need a big advance, they want to give you less royalty points, and vice versa.
Let's assume you get a tiny advance, say $3000. For royalty you can hope for as much as 10%, but might get only 7% for a first book. This percentage is calculated on *half* the list price of the book, since that's what the publisher sell it for (to the bookstores.) So, the worst case, the book sells only 10k copies, you get only 7%, and let's say the book only costs $20. Basically, you've been screwed, all that time and work, you'll earn only $7000 royalties plus the $3000 advance.
At 30,000 copies sold, and a 10% royalty, you'll be doing much better, $30,000 plus the original $3000, now it seems almost worth all those months of work. If your book is a 'general' topic that will not go out of date you could end up being published for a few years, and make some good extra money for years to come.
Some books can sell 50k, 100k copies! Do the math, it can turn into a lot of money. (Don't count on this as a first time author, lots depends on how the publisher intends to market the book. They'd probably push a book by Laura Lemay more than they would yours.)
Most publishers offer their proposal guidelines online, try this page at New Riders http://www.newriders.com/about/write/ - I have contacts here with the acquisition editors, but you'll need to have one of these form thingies filled out. I used a *wild* presentation on my first pitch to them, they need that info, but they don't need it in MSWord boring format!
Your pal, -doc-