I have split my reply into three parts:
1. some oft missed bits.
2. Kindle formatting.
3. Nook formatting.
1. Some Oft Missed Bits:Note: I have restricted specifics to the US and Canada as those are the markets with which I'm most familiar.
* register copyright.
Canada:
Application for Registration of a Copyright in a Work, $65.00.
USA:
eCO Online System, $35.00 online, $45.00 paper.
* if you get your own ISBN (International Standard Book Number) you will be listed as publisher as well as author. Personally I consider this a no-brainer. However, this is an area to be thoughtful and learn so you know what you doing and what you need.
A good primer:
International ISBN Agency FAQs, International ISBN Agency.
Canada:
The Canadian ISBN Service System (CISS): Free if published in Canada.
Note: of interest to Canadian Publishers:
Legal Deposit .
No copies need be deposited with Library and Archives Canada if 3 or fewer copies are made.
1-copy must be deposited if 4 through 100 copies are made.
2-copies must be deposited if 101 or more copies are made.
Library and Archives Canada supports the CIP (
Cataloguing in Publication program of cooperation between publishers and libraries enabling the cataloguing of books before publication.
USA:
R.R. Bowker ISBN Office: Price varies depending on how many you buy at one time. From US$125.00 for one.
Note: I would recommend buying at least 10 at a time (in US) for significant savings: 10 for $25.00 each, 100 for $5.75 each, 1000 for $1 each.
Note: of interest to US publishers:
The Library of Congress also supports the CIP (
Cataloging in Publication) program.
* once you have an ISBN you can either pay $45.00 (in both Canada and US) for a generated barcode OR you can do a search for a free online generator.
Note: the result must be clearly readable by a barcode reader.
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2. KindleIf you are publishing to Kindle Amazon has an entire subdirectory available to assist.

While, they say that they support several formats I find that many including PDFs do not always convert well.
See
Supported Formats.
You will note that every option has caveats listed. See below for my recommendations.
One of the links on that page is to
Simplified Formatting Guide.
Lots of great step by step information plus all the sidebar and other links.
Note: given our, Cre8, readers' likely expertise I would strongly recommend that you forgo Word and even PDF and code and upload as HTML (images in separate file to same location) ... BUT ... carefully read/understand the Kindle HTML defaults and exceptions...
HOWEVER: for ease of whatever both Kindle and Nook convert Word or OpenOffice .doc format quite well. Remember to remove all page numbers, page breaks, fancy fonts, etc.
Note: Because the displayed format flows differently depending on user's font-size, etc. you, as publisher, have no individual page control. You only set 'page' breaks at chapter endings. If you have not already realised that 'normal' page numbering is relative/subjective/irrelevant in ebook readers, well...

Yes, this can muck up things such as indices and Table of Contents - fortunately you can still set text anchors that work well.
The nice thing is that you can use Amazon's service to convert your work to Kindle readable format and keep to deliver to any Kindle readers who stop by your site. Of course it could be best to also publish (last step

) via the Kindle Store for wider exposure and some revenue.
Best for Last:
Note: recommend the KindleGen command line tool to convert their HTML, XHTML, XML (OPF/IDPF format), or ePub source into a Kindle Book. (part way down page)
Lower on same page: also recommend the Kindle Previewer which emulates Kindle on Win or OSX.
I still recommend uploading any tables, image captions, fancy font headers and the like as images. They are getting better at conversion but still not always quite right.
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3. NookNook uses the ePub format and has created
PubIt! to handle conversions et al.
Recommend reading
PubIt! Support and Resources Page. Especially the formatting section.
See the 'notes' in the Kindle section, much applies to Nook.
For those without a Nook and with a PC:
nook for pc.
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Last Note: Do NOT stint on the cover. It sells the book.Last Last Note: I have never used either (or any other) of the services mentioned in this thread (Calibre, SmashWords) but they are two of many; some are free, some are paid, some simply convert (with varying results depending on input) and others also secure ISBNs, etc.
Doing it all directly one's self is simple enough once one struggles - can you say ignoramous incompetentous? (not you of course

) - through the first one the process is straightforward.
It is no longer best practice to simply offer a pdf version. Now one should also cater to the popular readers particularly Kindle and Nook. And offering your creation in their online stores has several benefits...