How do we know we are smart?

I've just finished listening to a lecture by Jeremy Wolfe on intelligence, titled "How do we know you are smart?" The lecture explains how our brains work and how we've historically assessed intelligence. Scientists are discovering, however, that IQ measures are not the strongest measures of achievement (education, income, career). Rather, a much stronger correlate is how effectively a person integrates multiple areas of their brain. It's on iTunes University, if you're interested.
I'd love to hear from people:what makes you perceive someone as "smart" or "intelligent?"