Proofread, proofread, proofread

Proofreading is extremely important. Even if you think you are the best writer in the world, you should still proofread. The best thing to do is, after a paper is written, step away for an hour. When that hour pasts then go back and read it. That way your brain will tell you what you are really reading and not what it has memorized. Silly mistakes will most likely appear.