Please don't insult your audience, but make sure you make the experience pleasurable and interesting for them to hear or see your ideas. The screamer is always going to be there, because it's always going to work for someone, somewhere. You scream something long enough, some people will eventually listen, but it's not my choice at all. I hate screamer ads.

It sounds overly simple, but I clearly must understand who is selling the car. If I have to look for your dealership's name, or if I just saw your TV commercial and didn't catch who you were, or if I just heard your radio spot and can't remember who you are, you've just wasted your money.