What is plagiarism?
Plagiarism is --
Intentionally or unintentionally representing ideas or material from another work as your own
Failing to use quotations or to paraphrase correctly
Self-plagiarism is the publishing of your previously submitted published work.
What to cite
You should cite -
Any words, ideas, and materials that are not your own.
Exact quotes
Visual and audio materials
You don't need to cite -
Your own words, creations, ideas, etc.
Your own results from experiments
Generally accepted knowledge (like George Washington was the first president of the United States)