pore,
pour,
poor

A pore is a tiny opening in the skin.

Please pour me another glass of juice.

Rich is the opposite of poor.

principal,
principle

Our principal is a strong leader.

(The noun principal is a school administrator [your "pal"]; the adjective principal means “most important.”)

She asks students to follow this principle: Respect each other, and I’ll respect you.

(Principle means “idea” or “belief.”)

quiet,
quit,
quite

Libraries should be quiet places.

Quit talking, please.

I hear quite a bit of whispering going on.