I prefer a little circle by the action item and I fill in the circle on completion. A circle is quicker for me to draw than a checkbox. I can quickly scan the row of circles for open ones, and the completed items are still legible.
I use a yellow highlighter - Sharpie Accent Liquid. They don't bleed and the yellow doesn't fade.
Marking them off with a highlighter falls into the labeler camp for me. They both sound really silly and I'm continuously surprised at their positive impact.
I use my own set of symbols on my actions list (alle paperbased)
v = done
X = deleted, that means not relevant anymore
o (filled circle) = in progress
--> (arrow) postponed, some times a new date is written also