It really depends on the publisher and the market. In the 80s and 90s when computer programming for PCs was new, the fact that I could write and program made me a "hot commodity" for industry magazines for a little while.
One of my magazine editor recommended me to someone he knew at John Wiley & Sons (a Major New York Publisher) they helped me from there.
In general to get published do the following:
1. Go to Barnes and Noble or some other book store and find books like the one you want to have published.
2. Look at the publisher information.
3. Go to their web site and read their submission guidelines.
4. Follow their submission guidelines to the letter.
It will be a slow process and often painful.
Sometimes, they have a "call for papers" or something similar in their guidelines. This is what their market research indicates there is a demand for. If you can address that need and also follow their other guidelines, you will likely be "fast tracked" and you could get published sooner.