Prepositional use is the measure of fluency in English. "I think of you" You, specifically, are the person in my mind. "I think about you" I think about your personality or characteristics. Maybe this is more concrete: "I think of a number between 1 and 10" It will be a specific number, say 2. "I think about a number between 1 and 10" It could be any of them, 2 through 9 Admittedly, they can sometimes be very close in meaning. For example: "Whenever I smell apple pie I think of/about my Mom" But there is a difference: do you feel it?

Hi... Think of = opinion Think about = process or detailed opinion