Here is one of my favourite visual mnemonics.
I came up with it a long time ago, and now use it every time a student makes a mistake with this pair of words. I’ve never noticed them make the mistake again! (Note to self: reverse the colours next time!)
Since this was so quick to post, I challenge you to share your own favourite mnemonics, visual or otherwise, for those pesky mistakes students will keep making. I’ll add a list to this post as they’re published.