James Myers over on the Ogilvy blog says the only marketing rule that matters is “BE INTERESTING”.

to be interesting you have to all of the following.
(1) segment your market - create personas if we want to get digital about it.
(2) understand your customers requirements
(3) give them the personal treatment
(4) be relevant
(5) get to the point quickly
(6) ignore your (product) agenda until you know what the consumer wants

Read his post here.