To the Printers
Once you have your book in digital form, you need to find a printer. This means a little bit of shopping around. Do some research and find a few book manufacturers you might work with. Many printers normally handle only fliers -- make sure you're looking at book manufacturers, who have experience putting books together.
Ask for a quote -- a price for printing, that the manufacturer will honor for 30-90 days -- and request samples of similar work they've handled. Compare and contrast, and figure out who is offering the best results at the best price.
To ask for a quote, you'll need to decide how many books you actually want to print. Much of the cost of printing is in setting up the print run, so you'll get a lower price per book if you print more books at once. However, if you grossly over-estimate how many books you can sell, you'll end up shelling out a lot of money you can't make back in a reasonable amount of time. This is one of the most important business decisions you'll make, because it will directly affect your immediate profits.
Before the printer prints your book, they should print proofs -- essentially, printed test runs. When the proofs are ready, it's your job to check every page to make sure there are no mistakes. Anything that was not in your original file is a printer's error -- the printer must flip the bill to fix it. Any mistake that was in your original file is an author's adjustment (AA), which means you have to pay for it (though the printer may allow you a certain number of freebie fixes). After you've reviewed the proofs, you pass them on to the printer and they make the corrections.
At this point, or even earlier, the printer can print galleys (bound advance versions of the book). You can use these galleys to begin marketing the book.
Finally, the printer will actually create the entire run of your book, and ship the copies to your house, your storage facility, or wherever else you want them delivered (directly to a book wholesaler you have sold to, for example). It's time for the final step: actually marketing and selling the book.