I've read that if you were to send off a manuscript it's 250 words/ per page. So whilst writing in a mac pages document, should I section break at 250 words and start a new formatted A4 page, 1 inch margins each way in preparation for eventual manuscript send off. Should I write to the estimated 500 word count per printed page and section break? Or should I just write to fill the A4 page document and let potential publisher format it in future? How do I go about this?
The above, definitely. There is no way they want to see section breaks all over the place. In fact, they probably don't want to see any at all. They'll want sections markers; e.g., a # symbol. If you really want to estimate words per page, do realize that it changes for each publisher. It all depends on format. You can estimate it (if you're curious). Just check out a hardcopy of one of their typical books and count out a thousand words or so. Divide by the number of pages.
The 250 words/page was a measurement used in the days before word count tools, when authors submitted typewritten manuscripts. Now that we can find out exact wordcounts in a matter of seconds, everybody in the industry uses actual word counts rather than estimating it by 250 x number of pages.
