Intelligence varies person to person.
As we know, there is the standard system of intelligence that branches into many different categories; some may be intelligent when it comes to social gatherings, some may have prowess or skill in reading, others may be physically attuned to their body, etc.
Generally, the person we seem to view as being,"Smart,"is generally the more literate people, those who we consider knowledgeable and thus we believe we can learn a quantitative amount of information. These "Smart" people may be considered so potentially because of their good grades, because people have not branched into the information they have gathered, etc. However, they should realize they can just be as intelligent.
I believe intelligence in the way it is usually viewed is merely the branching off more into the logical side of things, looking past the simple, plaintive skin we see with out eyes and realizing relationships between different things. Realizing there is something bigger than us and that there is knowledge we can obtain that may not bend with our view, being aware that something could be deadly even if we feel we are "fine" or knowing something or discovering something that is passed our being "I". We seek knowledge first, then develop our view to wrap around it, even if it is not always the case.
Intelligence should be emotionless, or not based so strongly on emotion but more so on facts and good deductible logic.
In the broadest sense, I believe intelligence is merely becoming conscious of something, of some action, thing, object (whether it is our body, or why a force acts a certain way, or logically deducing why something is) that begins with curiosity or a question. True, not all curious people may be considered "intelligent", however they will collect knowledge and store in inside.
It all depends if the person is prone to making the conversation emotionally stimulating or intellectually stimulating.