There is much talk about Style Sheets. Copyeditors generally compile them for you, but they will all appreciate if you submit one to them to work with.
I honestly don't know much about them, I've seen a few and they were concise, detailed and interesting to read.
I've made a very basic Style Sheet, which I use on occasion, and if my novel (or series) is bought by a publisher, I will prepare a more detailed one to give to the copyeditor.
However, we can all prepare them ourselves, published or not.
Here is the download: BasicStyleSheet (PDF)
Feel free to pass it on, but I would like if you told people where you found it.
