Once all the formatting and features are finished, you are ready to convert your file into an eBook file. For Kindle you can use .mobi and for Nook you can use .epub. You can create both from the same initial Word file, so the entire process is very easy.
Save as Filtered HTML
The first step is to save your Word document as Filtered HTML. An eBook file is really nothing more than an HTML file, so by saving as one initially you've have done half of the work already. Saving as Filtered HTML preserves all the formatting of the Word document, but removes much of the tags that Word/Office use for their specific functionality, cutting down on file size and tags that have no place in an HTML file.
To do this, merely do a "Save As" in Word (F12) and in the Save as type dropdown at the bottom, select "Web Page, Filtered."
Below that dropdown, to the right, you'll see a tag called "Title" (which might say Add a Title next to it, or already have a title from your file in it). Make sure this is set to the title of your book. Select and change it if necessary.
When saving, save it two times – one with a filename that denotes it for Kindle, and one for Nook. That way you can convert each one separately in Calibre without any issues. If you want, update the type of edition in the Copyright Page for each to denote that one is the Kindle Edition and one is the Nook Edition.
Once saved, you can move on to conversion.
The software I've used to convert my books is Calibre. You can find out all about it on the Calibre website, calibre-ebook.com. It can be used as an eBook manager if you so desire, but I only use it to convert files. It's very easy to do, and it has the added bonus of being free. The conversion discussed in this tutorial will only use Calibre.
First of all, download and install Calibre. Once done and the program is opened on your computer, you'll notice that there are a lot of options and it may be a bit overwhelming. No worries, there are only a few steps you need to take.
Add/Update Your Book
The first step is to merely add your book to the list in Calibre. Click the "Add Books" button at the upper-left and navigate to and select the HTML file for your book. If you have more than one HTML file (if you saved one for Kindle vs. Nook), then add each separately. Anything added will appear on the eBook list in the middle of the main window, like so:
From there, you'll need to update your book settings so that everything is set for when you convert the file. Highlight the book in the list and select the "Edit Metadata" button on the toolbar at the top, or right-click and do the same thing. Either way, the Edit Metadata dialog will appear:
Make sure to update the Author(s) and Author sort textboxes appropriately. The Title and Title sort should be set, but update them if they are not. I believe the sort is only used in the Calibre list, but it doesn't hurt to be accurate with them.
This is also where you are going to attach the cover for the book. For publishing on Amazon or B&N, I suggest having two sizes of your cover: 600x800 and 180x240. The first will be used in the eBook itself, while the other can be used for uploading to the Amazon and B&N websites. In Calibre, select "Browse" in the Change cover section and navigate to your 600x800 version.
Also, remember to update the Date and Published fields to denote when you actually created/published the eBook file. Click "OK" when you are ready to save the updates.
That's really all you need to update on the file. Now you are ready to convert.
Merely select your book in the list and click "Convert" on the toolbar. It will bring up a Convert dialog, and if you already did all the updates mentioned in the previous section, there's only one thing you'll need to change. In the upper-right corner, there is a dropdown for Output format. Change this to the desired format – MOBI for Kindle, EPUB for Nook.
Once your desired format is selected, click "OK" to convert. It will take a handful of seconds to process. Once done, you can find your final file in the book's folder wherever you designated the Calibre Library to be on your file system (during installation of the program). That is the file you will use when submitting to either Amazon or B&N.
Verification / Quality Assurance
Before you submit, however, you should always check the file in the target eReader to make sure it appears as you want it to. Generally, if it looks good on Kindle, the Nook version will look just as good.
I do most of my checking on Kindle, since I actually own one. You can easily copy your file to your Kindle by merely plugging the USB cord that comes with your Kindle into your computer. Copy the .mobi file and paste it into the high-level Kindle directory where all the other books on your Kindle are. Disconnect the Kindle, turn it on and check out your book.
For help on transferring files to your Kindle, check here.
If you don't have a Kindle handy, you can easily check using the Kindle Previewer program, which can be downloaded here. It's a simple program that will open any compatible file so you can see how it would appear on a Kindle. Be aware that this is not the Kindle reader app for PC - you cannot add a custom book to that app. If you want to look at it on your PC or Mac, you'll need to download the Previewer application.
Change the font style or size. Test out the Table of Contents and the links there. Make sure all your special pages (Title Page, Section/Part Breaks, etc) look sufficient. Nothing will look that good in super-large fonts, so don't worry about those; just test the smaller fonts that most people will use.
Another important thing to check is whether the paragraph indents are working properly (based on the steps taken in the first post of this tutorial). Unfortunately, the only way to really know if all the formatting is okay is to actually read through the entire book on your eReader, making note of each instance that needs to be fixed (I do a final reading in this fashion, using the Note feature of the Kindle to mark areas for adjustment).
To test on Nook, I merely used the Nook app on PC and my Android handset. You can find all the versions here. Nook functions pretty much the same way – if it looks good on Kindle and the Table of Contents work, chances are it will work on Nook as well. But it's a good idea to try it out on at least one version of the Nook app (or the Nook itself, if you have one).
All that's left is to get them published on Amazon or B&N. I'll leave how you do that up to you... but hopefully someone has found these tutorials helpful in some way. Post a comment if you have any questions.
Shameless promotion: If you want to see how this all looks in final eBook form, download a free sample of my book in Kindle or Nook formats. You could also try reading it as well. ;)