Play 8 ball with them

Easy, just take a quick glance at the INT score on their character sheet

I think that the greater intelligence shows it self in making many and lasting connections between things which are not obviously connected - hence progressing human knowledge. It is not connected with remembering knowledge although both tend to occur together . I picture something in the brain wildy waving arround to try to connect to a different waving something from another retained thought.

You have to be smart enough to hang out with the right people. Folks just a little dumber than you. Which makes you smartest one in the room.

Being clever on paper means nothing really in the real world.

The examples you mentioned about being quantifiable made me think of things that Dr. Sheldon Cooper lacks.

Unless intelligence is on par with an Einstein, which few of us are, I prefer to measure people by their wisdom. Wisdom is equal parts intelligence, observation, and careful introspection.

It's highly contextual and relative. Need to define skills and talents separately. Their effective correlation with your environment can be considered intelligence.

A person good in spatial intelligence need not be good in other spheres like verbal intelligence and vice versa.

I am good in observation and I can identify small changes in people's behaviour to me but I lack in communication or expression so basically I fail to reciprocate to people in the way they want. Am I intelligent or not?

the ability to learn new things, and to accept when their knowledge is in error.

In my opinion, @Akfishlady nailed it regarding emotional intelligence ... highly under-appreciated. And while I greatly admire and respect pure savant-like intellect, I believe we've become so consumed with specialized talent that sometimes forget what it means to be 'well rounded.' Where are the Renaissance men and women today? The high IQ, artistic, athletic, engineering geniuses who have emotional intelligence?

Metacognition, curiosity. Other strong indicators..they've kept a journal from childhood, tend to be slightly OCD, often on the autistic spectrum, unconcerned with the opinions of others as they pursue their obsessive interests, usually cynical, skeptical, often atheist, often strong readers from an early age, think out of the box, usually humorous.

You know a bunch of cool stuff that's interesting to talk about while high

I thought it as about ‘processing speed’, so to speak, but I may be wrong.

I am intellegent, but I don't think I meet the grade for wht you are asking

Intelligence is the ability to extrapolate meaning and usage from information.

I'd say the ability to learn, welcome new ideas and think critically. The rest, like being good at math for instance, it's really like an elaborate game of trivia.

IQ tests were for children. French children to be precise. [123test.com]