I don't know how to explain the difference between effect and affect to someone. I've tried explaining that effect is a noun, and affect is a verb, that to affect is to make a change, and effect is the change that was made, but these explanations haven't made sense. (They're 17 and very intelligent, so please don't be rude.) Could you please suggest other ways of explaining this?
Effect can be a noun meaning the consequence of an action.
This drug has powerful effects.
It can also be a verb meaning to bring about.
The new principal effected many changes.
Affect can be an uncountable noun meaning the observable expression of emotion in psychology.
People with mental problems may have different affect.
It can also be a verb meaning make a difference to.
His presence affects her a lot.
I'd say the best way to memorize these very lightly different words is to associate them to something else that they would remember. You want to trigger this association so every time the moment arises that they need to use one, they can think for a moment and remember their mnemonic.
Since affect and effect are only one letter difference, try having that letter be what you grow off of.
(A)ffect when you want to apply, alter, adjust things.
You impact something else in a way. You're the cause.
(E)ffect when an it is the event (sort of). An explosion!
This is the outcome of what you've done. What you see. The result.
"I affected this firecracker by lighting it on fire, now wait for the effect when it explodes."
I'll try to come back and list more that comes to mind, but the logic is still the same that you need to make that connection that this word is like another.
(Sorry for the sloppiness, I'll likely revise this a few times within the next day)