Now that I've played around with it a bit, I feel pretty comfortable with formatting for Smashwords - and I imagine that I'll be able to transfer that knowledge to Amazon, as well. I'll give a few tips here, but I'll also try and release some sort of step-by-step guide soon (especially for OpenOffice users, who don't get enough love).
First of all and as I've mentioned before, use the nuclear option. Do not bother trying to work around all the crap modern word processors insert into your file - copy/paste it into notepad or another 'barebones' editor, and then past it back into Word or OpenOffice or whatever you use. This rids it of extraneous formatting, including italics underlines, bolded text, etc. I suggest you either go through and note where these things exist - or, even better, just do a close read after you've 'nuked' it, and decide anew where they are needed. Chances are you've italicized too much. I know I do.
A big problem with Smashwords is their improper treatment of page breaks. They don't seem to see a problem with letting your title page run into your table of contents run into your book run into your Coming Soon teaser run into your About the Author page.
I'm self-published, as are many of the people on Smashwords. We need every little trick to make us look professional because we haven't been vetted by some outside authority. Thus, the page breaks. Fortunately, and despite their own guide, there is a way to make Smashwords' Meatgrinder respect page breaks. Note: I found this at Paul Salvette's Blog. I reproduce it here for convenience.
Basically, page breaks can be made a part of a style. You can create a Heading style (I called mine "New Page Heading") that automatically inserts a page break BEFORE itself. Thus, if you make the heading of your TOC a New Page Heading, then it will appear on a new page.
The process is like so: Create a style from a copy of your normal heading style. For Word users, refer to the above link to Paul Salvette's blog post on the subject. For OpenOffice users (or, I imagine, LibreOffice users), navigate to Format->Styles and Formatting. Then click on the "Text Flow" tab.
You'll see a window like that pictured above. In the Breaks heading, check the "Insert" box. For Type select 'Page" and for Position select "Before."
There. Apply this style to your section headings, and they'll be sitting pretty on their very own pages.