"Think of" vs "Think about"???

What's the difference between "think of" and "think about"?

Examples:
He never thinks about other people.
He never thinks of other people.

She is thinking of buying a new car.
She is thinking about buying a new car.

I always think of you.
I always think about you.


Are they exactly the same?
If they have a different shade of meaning, what is it?

Hmm... I think those particular cases are equivalent.

The two phrases aren't completely interchangeable, however.

Husband: Shall we buy a new car?
Wife: Let me think about it. [Not "Let me think of it."]

Also, contrast these:
"It's time to think of some new ideas." In this case, the ideas don't exist yet, and we're trying to create them.

"It's time to think about some new ideas." The ideas have already been thought of and are about to be provided for the group's consideration.

- Kef

I think Kef's answer is very good, usually Spanish speakers, like me, hypercorrect ourselves avoiding 'of' because poor English speakers with Spanish as their native tongue use it incorrectly a lot of times. Maybe this is also true for Italian, French and other similar languages but I do not know if it's the same for Korean.