- Confusing its and it's.
- Confusing there, their, and they're.
- Confusing loose and lose.
- Confusing accept and except.
- Using apostrophes to pluralize (see the footnote for an example of improper apostrophe usage). (Apostrophes are not like confetti, as in "the more the better;" there are actual rules about when to use them.)
...aaaand I know I don't have a leg to stand on, seeing as how I confuse the words "left" and "right." (Yes, I do. I confuse them. I have to point with my hand when giving directions; my husband has to point when giving me directions.)
(And don't try to teach me how to remember left and right. I've tried all the mnemonics. Pointing is the solution...and drawing arrows in my turn-by-turn directions.)
(Ironically, I confuse the words but not the ideas. I have an excellent sense of direction. Inherited it from my dad.)
Here's an interesting Southernism: "ink pen." This rule seems to label this as a misuse, but don't forget the Southern accent: when Southerners say "pen" it sounds a LOT like "pin."
Improper apostrophe usage: Don't use apostrophe's for plural's.