How do you decide that someone is intelligent?

We must have an interior set of criteria that we apply to everyone we meet, and for some of them we apply the label intelligent or very intelligent.

What do you mean when you think someone is intelligent? Is it always a good thing? Is it an attractive thing? Can it be a scary thing?

Would you call yourself intelligent? Why or why not? Do you think that people who straight out tell you they are intelligent are telling you anything useful? Do you think they are bragging? Do you think they have a puffed up ego? Do you think they are accurate?