Affect and effect
Affect is a verb, although very rarely it can be used as a noun. Effect can be a verb or a noun, so it's no wonder most people get in a muddle here [Ed. I do!]. Try to use them both in situations like this:
Effect (noun): a thing that has happened.
"Seeing live worms in his dinner has such an effect on Brian!"
Effect (verb): to bring about change.
"We will effect changes to the school uniform from next term."
Affect (verb): to produce an effect on.
"Rachael shaving her head didn't affect the way Gabriel felt about her."