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.
Sandy Millin 
“make a mistake” – both “make” and “mistake” begin with M!
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And even, ‘mistake’ contains ‘make’: MistAKE 🙂 I use that one a lot too, normally with two different colours
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I do the same with the verb ‘to be’ versus ‘do’ or ‘have’ confusion. I am China = an outline of China with eyes, stick legs and arms. I am black hair = masses of hair with arms and legs… they also work!
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I find the following useful to remember how to spell ‘necessary’. Visualise a vicar wearing nothing but one collar and two socks 🙂
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