It's tempting to think of revising and editing as one task, but they are two separate tasks that require quite different approaches.
Revising is about the content, flow and organization of your paper. Is it clear? Are there areas that require elaboration? Am I addressing the topic or subtopic of my paper or have I diverged from the goal of the paper? Are like-ideas and supporting arguments grouped together in a way that will make sense to the reader? Are the ideas presented in a logical way? Revision is about making certain the paper has all necessary pieces and is solidly structured.
Once you've revised your paper, you're ready to proofread and edit. Editing is about the spelling, punctuation and sentence structure in your paper. Make sure there are no sentence fragments; that your sentences are grammatically correct and your sentence structure makes things clear and easy to understand.
Amherst College points students to several good resources and checklists on revising and editing:
Some of the links on this page may require additional software to view.
