I was taught it 30-something years ago. It certainly works - much like the method p describes for remembering the 'You and I/You and me thing.
The thing that people who just think I'm a grammar nazi don't get is that, once you learn these things, it actually hurts your soul when you hear them misused. If I hear someone say amount when they mean number, describe a company as a plural or say less when they mean fewer, it's like nails down a blackboard for me.