Proper documentation will help you avoid plagiarism and will empower you to:
You do not need to document if you're using common knowledge (e.g. the Declaration of Independence was approved by the Continental Congress on July 4, 1776), or if you're using your own thoughts, ideas, opinions, observations, or experimental results.
However, you must document whenever you copy (include a chart or diagram, for example), quote from, paraphrase, or summarize another author's work. This includes information from Web pages, books, songs, television programs, email messages, interviews, articles, artworks, or any other medium.3 A good paper should be composed mainly of your own ideas, citing various sources to support your argument.