Affect or effect? This is one I constantly doubt myself on, so I thought I'd share with you a few resources that help me. Grammar Girl has a great post that goes more into detail, or you can check out the video below for a quick explanation.
Grammar Girl's memory trick for affect versus effect:
"I remember how to use affect and effect by thinking of a big black raven. A raven? Yes, a raven! Because raven has the letters A-V-E-N in it, and those also stand for
Affect: Verb Effect: Noun
Fix that image of a raven in your mind, and you’ll always remember the most common way to use these words."