A small reference notebook
Give a working draft one clear purpose
Name the reader's task
Before editing individual sentences, describe what the reader should be able to do after reading. That purpose gives a useful test for each paragraph. A paragraph that serves a different task may belong in another document rather than in a longer introduction.
Put the main point early
Readers should not have to reconstruct the conclusion from a collection of background details. State the point, then add the evidence needed to assess it. A concrete example is often more useful than another sentence explaining that the subject is complicated.
Revise in separate passes
First check whether the structure follows the task. Next check whether each paragraph develops one idea. Then remove words that do not change the meaning. Separate passes make it easier to notice a structural problem before spending time polishing the wrong sentence.