The single best thing you can do to improve your grade on a paper is to produce and have reviewed a draft of that paper.  Even better is to produce several drafts of the paper.  A paper draft is NOT an outline, NOT the introductory paragraph, NOT an annotated bibliography.  It is the full text of the paper.  By producing such a draft as early as possible in the writing process, you not only provide a good writing sample for review by your professor or other reader, you also produce a document which allows you to identify those areas of the paper which need your immediate attention – areas which need deeper analysis or additional research.  By providing your professor with a draft (or two or three drafts) you are allowing him/her the opportunity to clearly articulate their expectations for the paper and receiving guidance on how to improve your writing skills.  The importance of drafts cannot be overemphasized – almost always, submitting drafts of written works will raise the final paper grade, assuming of course you follow the advice of the reviewer.