Proper formatting is an important aspect
Idea is wonderful and the story is well written, then what about the formatting. If the reader is not able to read properly, do you think it is going to win laurels for you?
This aspect of self publishing is very less talked about but this is nevertheless a very important aspect.
Usually a good self publishing company has skillful people to do the formatting part. But one needs to know the nuances of it to make a good writer. The font size and type should be readable. So not experiment much with the font. The most popular font is Times Roman and Arial. If it is a e-book, then you can try verdana style of formatting.
It is the best practice to start a new chapter from the right side page. This is most comfortable and accepted style. Writing chapter number at the beginning of each chapter is a little outdated style. Mostly ghostwriter try out new ways of introducing, may be the first word or the letter can be bold with large size.
Paragraphs should not be very long, otherwise interest of casual reader are usually lost. Also sentences should be not very complex and one sentence should have one idea. Otherwise it is a burden for the reader to understand. And everyone wants to enjoy the book and not struggle over its readability and understanding.
Sit with the person who is formatting your book to ensure these points, they can make or mar the sale ability of the book, because the first impression is the last impression.