When playing evil, overacting often comes.
Not the best poetry but certainly a truth I encounter time and again at all levels of acting; people trying to "play evil". I have even been asked how to go about "playing an evil person".
Answer: You don't. Ever. You never play evil.
As with any character, you find a motivation for a scene or a play. You give them a personality, you add meat to the bones the writer has given you. And you proceed to become that character. It is the goals and motivations and choices that the character makes that will determine if he is evil or good, so you need to be convincing when you lead your character through those choices. Because to him, it is not evil, it is expedient.
I keep this week's article deliberately short and to the point in order to hammer this very important point into the brains of any would be actors. Elaborating on the point will only make it more theoretical and less practical. This is a pet peeve of mine, and I won't risk inflating the issue.
Find what you character wants. Bring him to life. Let the audience decide on what is evil, and what is not. Period.
Moustache twirlers need not apply.