Sonia Simone at Copyblogger hits the nail on the head:
Quit thinking of brands in terms of logos or typefaces or what a particular shade of blue communicates to your customer....
To work as a brand, a promise has to be exciting. It has to mean something to your potential customer. It has to turn everyone on — you and them.
I would even add that your brand is internal as well. While much of your brand is seen and felt by customers and prospects, your staff sees and feels it too.