Seth Godin has created an attitude profile for marketers. Marketing is a balancing act between science and emotion, with passion as the main driver. I would be looking for exact the same person as Seth...
Traditional job requirements: show up, sober. Listen to the boss, lift heavy objects.
Here's what I'd want if I were hiring a marketer:
You're relentlessly positive. You can visualize complex projects and imagine alternative possible outcomes. It's one thing to talk about thinking outside the box, it's quite another to have a long history of doing it successfully. You can ride a unicycle, or can read ancient Greek.
Show me that you've taken on and completed audacious projects, and run them as the lead, not as a hanger on. I'm interested in whether you've become the best in the world at something, and completely unimpressed that you are good at following instructions (playing Little League baseball is worth far less than organizing a non-profit organization).
You have charisma in that you easily engage with strangers and actually enjoy selling ideas to others. You are comfortable with ambiguity, and rarely ask for detail or permission. Test, measure, repeat and go work just fine for you.
You like to tell stories and you're good at it. You're good at listening to stories, and using them to change your mind.
I'd prefer to hire someone who is largely self-motivated, who finds satisfaction in reaching self-imposed goals, and is willing to regularly raise the bar on those goals.
You're intellectually restless. You care enough about new ideas to read plenty of blogs and books, and you're curious enough about your own ideas that you blog or publish your thoughts for others to react to. You're an engaging writer and speaker and you can demonstrate how the right visuals can change your story.
And you understand that the system is intertwined, that your actions have side effects and you not only care about them but work to make those side effects good ones.
The cool thing about this list is that it's not dependent on what you were born with or who you know. Or how much you can lift.