Here are some ways I would use think of / think about:-
What do you think of his new car? ( Do you like it?)
What do you think about his new car? ( Do you have an opinion? Was it a wise purchase?)
What do you think about when you are alone?
What do you think about the world economic situation? (think of is also correct, but think about is asking for more of an opinion)
Can you think of a fruit starting with the letter �A �?
I want you to shut your eyes and think about an apple. (Colour, size, shape)
Seeing daffodils makes me think of my mother. (She grew daffodils)
Seeing daffodils makes me think about my mother �s garden. (More detail, the garden, my mother, her home)