Skidmore Guide to Writing Index
Don't use slang or colloquial expressions.
Example: The little kids who go to the local day care center are totally cool to be around. It's awesome to see how things that would seem gross or weird to guys in the dorm seem perfectly okay to them.
In college writing, "little kids" are "children;" "totally cool" may be "interesting," or "fascinating"; nothing is "awesome," "gross," or "weird." "Guys" might be "students" and "perfectly okay" may be acceptable. Your readers will expect that your written work will be on a higher level than informal conversations with friends.