One of the most important parts of formatting your book to prepare it for Smashwords seems to be the copyright page. It's mentioned in the guides a number of times. Books won't be accepted into the Premium Catalog without one. It's important to claim your work as your own and also make clear what your policy is regarding sharing and/or distribution of your work.
You can place your copyright information on your title page or you can dedicate a page for this alone. I personally prefer to flick through as few pages as possible before reaching the beginning of the story itself so I like when this all fits on the one page together. I also dislike images in Ebooks so avoid these also. If you are going to create an Ebook then I would advise you to read a couple - it won't take long before you see what kinds of things could be irritating to a reader.
The copyright section - which looks better if centred - should contain something like "Published by (author name/publisher name) at Smashwords" or alternatively, "Smashwords Edition." You can say something like also published on Kindle (or wherever) but you should always name that particular copy as published on Smashwords. You are allowed to mention if it is published in print.
Some people like to link to some other books they have published on Smashwords, to their author page, their website or their blog. A lot of people seem to put this on their copyright page. Others show this information at the end of the book. If people enjoy your story then they may be keen to read more of your work so it is a good idea to give them some kind of contact information. Obviously, Smashwords aren't keen on people linking to their competitors.
If you aren't sure how to hyperlink to other web pages in your document, this is how I did it. I copied the website address, typed the title of it into the document (for example, my blog) then highlighted this title, right clicked and selected hyperlink then pasted the web address into the space provided. It looks much nicer and more professional than using a full web address.
Now you need to add a license statement to your copyright page. Smashwords books are DRM free so they have no copy protection or encryption. DRM can be a pain for purchasers but without it, you'll have to trust people not to pirate your work. Adding a license statement is a bit of hint to prevent accidental piracy. There are two statement examples in the style guide, one for authors who don't want people to share their work and another for those who are open to people sharing the book with their friends. You can use either of these statements or adjust one of them to make it personal.
Follow the style guide as much as possible, there is so much information (as well as examples) that formatting your book for submission won't be as complicated as it may sound.