English is such a confusing language, filled with rules that are constantly broken! We were taught "clues" in school to help us remember which spelling to use. Stationary has an a, like nail, so you can think of a stationary object as something that is nailed into place. As for principle and principal, the clue was 'the Principal is my pal'. As for lie and lay, a clever college professor taught us that 'you don't look to get lied, you look to get laid." (Lay is a transitive verb that means to put something or someone into a reclining position.)

Personally, I cringe when I hear pacific for specific. So many people do that when speaking!