Here's another tip from Bryan A. Garner's The Winning Brief: 100 Tips for Persuasive Briefing in Trial and Appellate Courts.

Garner recommends writing down a draft un-selfconsciously to the end, and only considering revisions afterwards. Don't risk losing momentum to choose exactly the right words. Writing rapidly is a good idea so long as a review for necessary changes takes place later. Nothing is wrong about waiting to correct a bad sentence while letting the ideas flow freely. An outline can serve as a map, as one tries to write as if speaking aloud. Doing this should help the words convey greater swiftness of thinking, and avoid making them laborious to read.

It's a also good practice to allow some time to pass between drafting and the editing.