Effects or affects? Which is the noun and which the verb?
To find the answer, just think of the phrase special effects: The second word starts with the sound ef. You'd never think of saying (or writing), "special affects," as a noun, would you? Since effects functions as a noun in this instance, just remember that it works that way in most other instances, as well - except when it means to cause. In that case, it's a verb: One effects (or causes) change.
Similarly, affect can act as a noun occasionally: Someone's affect refers to that person's observed emotional state.
Those are exceptions to the rule, but try not to get hung up on them. They're not the true source of the confusion. The real problem is that we think they sound alike, so we forget which one goes where. And when we speak quickly, they do sound alike. They both come out as uh-fect, just as February tends to come out sounding like Feb-yu-wa-ry and often winds up as aw-fun.
It takes careful enunciation to reveal that effects (think FX, as in the FX Channel) doesn't really sound like affects (uh-fects) at all. If you remember that much, it might affect how well you remember overall rule. When in doubt, just consult your TV listings.
It's not a special effect, it's just proper usage.