I didn't come up with this myself, I read about it a long time ago somewhere on the 'net and I can't remember where/who (sorry). I thought I'd pass it along though since it's a great idea.
Some boards and LCD screens will continue to be powered through the USB cable even when you turn your 3D printer off, which is particularly annoying if you're using something like OctoPrint. The simple solution is to get some electrical tape, cut a small thin line of it, and cover the 5V connection in the plug. Here's a picture to help you:
