Write actively. Using a passive voice indicates disinterest on your part as an author, and your audience also loses interest. Use active voice to make your writing more direct and engaging. In the active voice, the subject performs the verb, as opposed to having it performed on, to, or by them. For example, "The car crash made Josh late," is active. "To be on time, Josh will have to avoid crashing," is passive.
Use positive phrasing instead of negative. Negative statements typically involve more words; conciseness adds value to your writing. For example, instead of "She could not remember," use "She forgot."
Form sentences carefully, ensuring that phrases and punctuation make sense. For example, "The panda eats shoots and leaves" is incorrect. The sentence should read, "Pandas eat shoots and leaves."
Expand your vocabulary. No one wants to read the same words in repetition. A dictionary or thesaurus assists in varying your phrasing.
Proofread your work. Do not rely on spell check; it will not help you avoid common homonym confusion. You may spell affect/effect, their/they're/there or your/you're correctly, but have the incorrect word choice in your writing.
Watch your modifiers, adjectives and verbs. Keeping your language concise indicates sophistication in writing. For example, use "shouted" instead of "they were hollering loudly" or "overcast" instead of "the sky was somewhat cloudy."
Cite your sources. Use Strunk & White's Elements of Style, MLA, APA or Chicago guidelines (unless your instructor chooses another style) to find and cite references to reinforce your position or statement.
Verify assignment instructions. Many professors have specific guidelines for research paper parameters, and understanding what the professor expects helps you to attain the best grade possible.