The best have emotion, quirkiness, humour, humanity and difference. The worst shout, talk down, and inspire you to hit 'mute'. 15 or 30 seconds is only enough time for two concepts at the most. To stand out in a block of commercials, state your case in a considered and clear way and, most importantly, know what your case is. Like all advertising, know your point of difference and tell that story well.
My experience as a stills photographer helps me to shoot commercials, as every shot is as considered as a still frame. And I can also shoot the stills!