Get to the point. Edit over and over again. Read your paper aloud to sound out problematic style or content. Look for information that requires documentation. Edit for fuzzy thinking and for vague connections.
Writing is extremely hard work.
Keep back-up copies of your work on a floppy disk or other storage device. Read my comments carefully. I intend them as aids for your ongoing improvement as a writer, not just as a means of giving you a grade. The following are the criteria for the various grades as I perceive them. The A paper is outstanding.