Although it feels cliche to say it, editing a research paper is a lot like clay sculpting. While writing is the process of getting your clay of ideas to a point where everyone can see them, editing will be the last few steps of presenting that clay in the best possible light.
If you've written your research paper well (see my other article for that), then editing is simply going to be refining what you established writing, without re-writing.
There is no perfect way to go about it, but there are some techniques for making improvements that I'm going to show you. There are three critical points of your paper that can win or lose the reader:
How Your Supporting Paragraphs Work With One Another
Your paper needs to have a flow to it, from beginning to end. This is done primarily by how your supporting arguments work together. Another way of saying this is that there should be no extraneous information or digressions.
In general, it's best to save your most sophisticated points for last. Refined ideas will need more introduction and supporting material, but they also add more clout to your paper. Demonstrate that you've put in a good deal of thought on your topic and you'll get a better grade.
This doesn't mean your first points can be boring. You need to engage and introduce the reader to your line of thinking and why it is correct very early on. You'll find that the best papers keep the reader constantly engaged, with every sentence working for the next.
It's difficult to find flow on your own. After all, you came up with everything, so it's easy for you to follow your own writing. For this reason, use peer review to find out what others think of your paper. This will immediately help you pinpoint any areas of confusion.
A Terse Introduction
What should your introduction accomplish? It has to provide the backdrop for you to introduce your thesis. You need to provide just enough information to state your thesis, while also being interesting.
Your biggest enemy here is writing too general of an introduction. You need to get straight to your thesis, and talk about only what's relevant to your argument.
A great way do this is by entering with a common theme or area of study regarding your topic. Bring up what a current area of research or theory on your topic before make your case. It's best if you use this reference as a primary source throughout your paper.
A Thoughtful Conclusion
Conclusions get tacked on more than I care to mention. A thoughtful conclusion will make you stand out from the rest and get you a better grade. Here are two ways to do that:
Leave the reader with a question. Now that you've explained your entire argument through exposition, what else is there? Is there a further development to your idea or conclusions? Reiterate your thesis now that you've given the reader your supporting statements, and why it's important.
Leave with reader with an ultimatum. This is just one final bit you give the reader to keep them thinking. What are the implications of what you've said? What are the ultimate consequences of your argument? Lay it out here.
Run through these three steps with every paper before you turn it in. I guarantee you'll see better results.