Probably the easiest way is to end the one chapter on one sheet of paper and start the next chapter (with a chapter heading, like Chapter 16--or whatever number chapter it is) on a new sheet of paper.

Your slug line goes left justified at the top, the page number goes in the right corner. Use a header to do this saves typing it on every page and makes it even. Then a third of the way down you put Chapter X , drop two lines and put in the chapter title if you have one, then go down 4 lines and start the chapter. Use Times New Roman or other clear dark font, in 12pt and 1 to 1 1/2 inch margins on all sides.

Most times the words Chapter X are underlined. If you have a word processing program that lets you see line numbers----the chapter goes on line 6, and the text starts on line 9 of a double spaced mss---just remember to turn it off when you print it. Don’t use the keep it together features---widows and orphans protect. If one page has 22 lines of text then they all should, except the last chapter page.

I center the page number at the top and put my phone number in the right corner. I also sometimes tinker with words if I end up with only a line or two on the last chapter page. It just looks funny to me.

Jeremy, editors use the space above short story titles and above "chapter 16" to write notes to the typesetter, so it's a good idea to leave them some for that.

Publishing is moving very slowly toward more technological things, but it isn't moving there nearly as fast as the rest of us are, and most editors have learned how to do their things in a very untechnological way.

The more the author can do to help the editor do the job the way the editor knows how to do it, the more professional the author is going to appear to the editor, and the better the editor is going to feel about working with the author.