A little-known fact among beginning writers is that revision and editing are two entirely different processes, both of which are essential to effective writing.
Revision is the process of seeing the paper again, as if it were something new (re-vision). During this process, the writer looks at larger issues which affect the structure and meaning of the paper. Does the paper have a unifying main idea? Do the examples and details in the paper support this idea? Are the examples and details developed enough, or do they leave the reader to figure things out? Is there a logical connection between the supporting ideas, or do some parts of the paper seem unrelated to the rest? Is the introduction interesting? How does the conclusion work? How will the paper affect a reader? Will the reader be able to understand it? Is the language clear and concise, or is it wordy?
Editing, on the other hand, is simply proofreading. When you edit, you correct problems like typos and grammatical errors; you read through the paper line by line and make simple changes. Generally, editing occurs when the paper is considered a finished product, almost ready to turn in.
Editing is a matter of remembering which errors to look for. Essentially, the process is the same for every piece of writing you create, so all you really need is a good checklist. Paying attention to the kinds of errors you make most often will help you create a list which suits your needs. With practice, you may be able to internalize your list so that you no longer need to look at it as you edit.
Revision, on the other hand, is a skill which takes some practice to develop. Each time you write, there will be different concerns, and it takes time learn what questions to ask yourself about your paper or what kinds of input will be helpful from a reader. The following documents will give you some ideas to help you get started. As you practice revision, you will develop a sense of what works best for you.