Affect and effect are probably two of the more confusing words in the English language. Or should I say the use of them is the confusing bit.
A general rule of thumb is that affect is usually used as a verb, and effect is usually used as a noun. As with other parts of speech, when in doubt try to replace it with a word you know the function of (i.e. clearly a verb, or clearly a noun); if it still makes sense then you know which one to use.
Example: “The arrow affected the aardvark.” “The arrow injured the aardvark.” Injured makes sense here, so you need the verb form.
Effect is a noun, so try to replace it with another noun, e.g. “outcome.”
Example: “The outcome was eye-popping.” If you place these substitute words in the other sentences they wouldn’t make sense.
I hope that helps! If you’re confused, just think of the aardvarks…
Stephanie Huesler 
I relate the word ‘affect’ to the word ‘action’, since they both start with ‘a’. Affect is an action, (verb) while effect, as you say, is a noun. Simplistic I know, but it’s one of those little things that help us remember.
That’s also a great mnemonic device! Thank you for sharing it with us! 🙂