Multiple layers
Instead of drawing all the layers, you may consider using a bolded arrow. However, avoid doing it, unless you really have no ability to do so.

Repeat
Robert Lang suggests using a line to point to the specific flap that you want to be repeated, instead of using an arrow with a dash across it.
My opinion is that, if you want to repeat for just one flap only, you use Lang's method. But if you are performing pleats, repeating it with all the layes, or repeating on the back (both back and front have one flap only), then I suggest that you use the later. In the second case, the number of times the step(s) is/are to be repeated, e.g. 5 times, then there should be five dashes across the arrow. However, if you use the arrow method, you should write clearly which steps to repeat. As for the line method, the line must coonect to a box with the instructions of the steps to be repeated.

Diagramming
If you want to publish an origami book, you should follow these suggestions:
1) Use the same set of symbols throuhout the book.
2) Make the diagrams look clear and tidy.
3) The reader mus know what the diagrams mean.
4) Contain text if needed.
5) Include a chapter on symbols used in the book.
6) Show the coloured and white sides.
7a) Make the diagrams "look alike". e.g. black=coloured/primary colour, white=white/secondary colour. Do not swithch to other colours.
7b) (text). Make the text clear. You must be grammatically correct, and choose to use a lot of text or just some.
8) Use same text design. (fond, size, etc.) Note: More info on text design are at Robert lang's diagramming page. You should decide on where the text should be located.

Using the names of symbols and folds
Much of these have been covered by Robert Lang. However, just a few reminders (these info may also help readers):
    You can call the Preliminary Fold a Preliminary Base. Avoid calling it a Diamond Base. Use the same name throughout the book.
    Some people call the inside reverse fold a "pocket fold". Use
the actual name.
    Some people call the outside reverse fold a "hood fold". Use the actual name. (Come to think of it, the nicknames are reasonable. "Diamond Base" may seem better, since all traditional bases are preliminary. But stick with the traditional names.)
    Do not replace an old symbol with a totally new one. That dies not mean you cannot modify the symbol. Creating more folds will lead to confusion.