Most college essays should be written in formal English suitable for an academic situation. Follow these principles to be sure that your word choice is appropriate. For more information about word choice, see Chapter 4 “Working with Words: Which Word Is Right?”.
Avoid slang. Find alternatives to bummer, kewl, and rad.
Avoid language that is overly casual. Write about “men and women” rather than “girls and guys” unless you are trying to create a specific effect. A formal tone calls for formal language.
Avoid contractions. Use do not in place of don’t, I am in place of I’m, have not in place of haven’t, and so on. Contractions are considered casual speech.
Avoid clichés. Overused expressions such as green with envy, face the music, better late than never, and similar expressions are empty of meaning and may not appeal to your audience.