I have some rules of thumb about writing research papers that I can actually articulate. For example, leave all definitions as late as possible (but not later!), so the reader won't fear "Do I need to understand this definition for this theorem?" nor wonder "Did I understand that theorem, insofar as it didn't seem to use the previous definition?"

One I don't have, though, is where to include paragraph breaks in proofs. If I follow the usual maxim that each paragraph should be about a single idea, then interpreted variously, this leads to sentence-long or page-long paragraphs.

More specifically, do you think of "It remains only to show some big thing" as an announcement with which to begin a new paragraph, or as a capstone with which to end the previous one?

Do you have a maxim describing where to put paragraph breaks in proofs, that doesn't lead to ones that are too short or too long?