Write early; revise often. Papers improve with effort.
Read your paper out loud. If your tongue trips over a sentence, rewrite it till it comes off easily.
Search again. As you see what you are writing, you may need more information. This is normal -- it doesn't mean you searched badly, it means you're learning enough to ask good questions.
Ask for advice. Talk with your professor, visit the Write Spot, discuss with your classmates. You may have good ideas, but part of the job of writing a paper is to learn how to communicate those ideas to others. Bouncing your ideas off many minds helps a lot.