It is often a dream or a distant goal to have your own book published, in print, in your hands. The internet and print on demand have changed that dream into a reality for many, and the process is creating many authors every day. I used Lightning Source for this process, but you could technically use these same steps with any printing service.
The first step is establishing an imprint or publishing name. With the printing service, you are considered the publisher for purposes of who is in charge of the title. Since you are the publisher and the author, you retain all of the profits that are not given to the printer for printing and binding the book. In order to become a publisher and in order to use many printing services, you MUST purchase ISBN numbers to assign to your books. ISBN numbers are a universal cataloging and index number that is unique to every book that is published, similar to a social security number for a person or a VIN or license plate for a vehicle. Some services do give you ISBNs for a low cost or for free, but you will not be listed as the publisher of record. Determine whether or not this is important to you before you proceed. (It was important to me.)
Once you have acquainted at least one ISBN, you should update the information for that ISBN on the MyIdentifiers (Google MyIdentifiers or US ISBN Agency) website with the title's information. I would recommend being as complete as possible, as I had a problem with updating the ISBN information close to the release date of the book and that caused a consistency problem across the retailer websites.
After you have finished those steps, you are ready to apply for an account at Lightning Source (if that is who you are using). Be as detailed as possible with your application, and be sure to be honest. A common misconception that I've heard is spreading around is that you must promise to publish a certain number of titles before Lightning Source will create an account for you, and this is incorrect; be honest with them from the beginning. If you will be publishing a book or several books with them, you will want to maintain a positive working relationship with these people. You will likely go through a process of interviewing with the Lightning Source people through email, and they will have you fill out contracts and forms both online and offline. You will need access to a fax machine to send signed copies of the contracts back to them. Be sure to read the contracts carefully so that you understand what they mean. Lightning Source is not out to scam you or steal your money, but you need to comprehend the terms on the paperwork and understand how they publish books.
If you are using a different service, you should carefully read all contracts and agreements. If you agree, sign them and send back (or submit through their process). If you do not agree or understand, consult an attorney.
When I established my account, I decided to complete the paperwork for all processes at one time, even for things I did not intend on using, so that they would be an option if I ever chose to use them. The service that I am talking about is being able to accept returns on books so that they can appear on bookshelves in brick-and-mortar bookstores. I have no intent on going that route at this time or in the near future, but I filled out the necessary paperwork so that I could if I wanted to do so later.
Once the account is setup and ready to go, you can begin uploading your files. If you are using Lightning Source: Ingram has operation guides on their website, and I thoroughly recommend reading each one that applies to your project at least 20 times before uploading. You must make absolutely sure that the files are correct before you upload, or you will have to pay additional charges to change the files later. The setup fee is $ 75.00 to begin with, and each revision can tack on additional costs to that. Minimize your liability early on by proofreading everything thoroughly and making sure your cover is formatted properly before uploading. Once common mistake that people make is not uploading the content and the book cover in the correct naming format, and it is the easiest mistake to fix. The cover should be YourISBN_cov.pdf, and the content should be YourISBN_txt.pdf. You can omit the underscore _ if you choose, but they must be formatted in this way. Like I mentioned earlier, read the setup documents thoroughly even times until you are sure you understand them.
If you are using a different third party printer: You should check the setup costs and other fees before you start the process to make sure it will be possible to complete the process and get the book out there.
Once you have submitted your files, you can order your proof. This is a required step for first-time authors, but it is recommended to receive a proof each time you upload a new book to check for errors and inconsistencies. The price is (as of this writing) $ 30.00 for a paperback and $ 35.00 for a hardcover at Lightning Source, but it can vary among different printers, and the only shipping option is 2nd day air (which is the cause of the increased price). For this reason, I recommend uploading a new book on Monday or Tuesday so that Ingram and UPS have a lenient amount of time to produce and ship your title without days falling into the weekend and delaying it until the next week. Other printers may have different speeds on shipping time and book printing and binding, and they each should have the information available for you.
Once you receive your proof, check over it for errors that may need to be corrected, and, if you're happy with everything, submit the title for distribution. It can take anywhere from a day to four weeks to show up in the distribution channels. Barnes & Noble and Amazon seem to be the fastest at discovering your title. Barnes & Noble will actually list your new title based on the ISBN information alone, so, as I said earlier, try to make sure it is 100% correct the first time you enter it. When you have approved the title and it enters the distribution network, you begin your sales and marketing process. Good luck with your efforts, and I can answer questions if you have them!