Don't procrastinate. Your professor will be able to tell whether you've carefully meditated upon your topic, or whether you threw together a "good enough" paper at the last minute. On the first day of class, review your syllabus and note when papers are due. Set researching, writing and proofing time into your schedule. Review your schedule daily so your deadline doesn't sneak up on you.
Research your topic thoroughly. Become an authority on the subject. Talk about your topic out loud. Explain it to people. Take notes as you meditate upon the subject. Investigate numerous sources and gather a well-rounded array of information.
Use your own ideas when you write your paper instead of filling it with quotes from other sources. It's alright to use quotes from time to time as an introduction to your own ideas, but don't let someone else's words take up more space in your paper than your own.
Write the way you talk. Your professor will not be impressed if you fill your paper with big words you had to look up in the dictionary. There will be situations in life where you'll have to fake it until you make it, but your paper isn't one of them. Impress your teacher the way you would a first date. Be yourself.
Cite your sources properly. Give credit where credit is due, even if you haven't quoted the source exactly. If you're using another person's sentiment or ideas, acknowledge it.
Reach the assigned page or word count without pulling any tricks. Your professor knows them all. Don't increase the font or change to a larger type; don't increase your spacing or shorten your margins. If you give yourself enough time to complete the assignment without rushing, you'll have plenty to say.
Finish your paper, wait a few days and then read it again. Ask yourself, "Is this paper as good as I thought it was?" Have someone proofread it before you turn it in. They might raise points you hadn't considered or catch mistakes you missed.
Hand in your paper in a neat and clean condition. No food stains, coffee rings, water marks, crumples or tears allowed.