Affected can be used as a past tense verb that means influenced or changed. It can also be used as an adjective to refer to a noun that has been affected (the affected body part). Effected is a past tense verb that means brought about or achieved. It's a very subtle difference from affected.

Is someone affected or effected by something?

"Affected" means "impacted, created an effect on, changed in a certain way." "Effected" means "executed, brought about, produced something."

Did the cold affect or effect you?

The verb affect means “to act on; produce an effect or change in” as in The cold weather affected the crops (it produced a change in the crops … probably killing them). ... So, when you're looking to use one of these two terms to express an action, chances are you're looking for affect.