Of all types of books you may consider writing, the "how-to” guide is the easiest to sell. Matter of fact, I'm willing to guarantee you can find a publisher for your efforts, if your book is written in easy to understand language, and has good illustrations.
Notice I didn't say anything about subject matter. Just about anything you can think of can, and should, have a book written about it. My favorite approach is to take one of my personal projects and turn that into a book.
For instance, I have built computers as a profitable hobby for years. My latest book, "Building a PC for Beginners” grew out of that. But your book could be about anything.
Perhaps you have a home improvement project in mind. You might be wanting to install a laminate floor, let's say. Now, you may protest that you are no expert at this, but that doesn't matter. People enjoy reading about the first time efforts of others. If you make mistakes as you install the floor, tell about them, and tell how you fixed them, because the odds are that other people are making the same error.
Take lots of photos as you put in the floor. Show the different steps of each process
Keep a daily journal of what you are doing. Write down all that you have done, at least in the form of notes.
When the project is done, you will have both a photographic record, and a written account of what went on. Take the notes, and flesh them out, using your photos to help remember how things were. Add captions to your pictures, and the first draft of your book is done.
Read through it, clarifying those parts that need further explanation, and cutting those that are redundant. This second draft should be checked for typos and small inconsistancies that can easily slip past. Having a friend help you at this stage is a good idea.
Now, you're ready to send it to the publishers. Congratulations! You've written a "how-to” book!
Michael Quarles wants you to look at his website http://www.monkeyseemonkeydobooks.com