The first mistake most ad-makers fall into is they try to come up with ideas that their partner likes.

This is not a suggestion that you become an intransigent jerk. (I’ve tried that. It’s neither efficacious nor much fun)

Rather this is a suggestion that in coming up with ideas you realize that what you’re after isn’t something that’s been done before that is easily comprehensible by others, but something that hasn’t been done that sounds impossible, looks difficult and feels implausible.

The most important place to look is where other people don’t.

In order to make a great ad (or any piece of communication) you must first have something to say.
If you find that something to say in a place other people haven’t looked, what you’ll say will more likely demand attention than will something said by someone who has looked in the same places everyone else has.
Great ads open windows in people where they didn’t think windows could be.