This is a very difficult question, because thinking is so much of an individual thing that I never have really thought about how I could teach it. There is no one “correct” way to think, nor any incorrect way for your brain to process information. So I have to say if I was charged with teaching a child to think , I would take how they already think and help it grow. To teach them how to “properly” think the way I believe to think would take away their individuality and conform them. However I would steer them away from thinking violent thoughts, by giving them things to think about.
Next I would show them things how my chemistry teacher does, by giving them the reactants (or the steps before solving the problem) and how I get to the products (or the solution of the problem). Then I would give them another set of reactants, and have them reach the products on their own. This way the child can discover on their own how to find the answers to things in life, or school whatever the case may be. I would play timed, educational board games with them, such as Scrabble or chess , to sharpen their thinking and the quickness of their brain. Also, I would ban mindless shows, such as the ones on Disney Channel, and encourage the History Channel, or KERA’s children shows, such as Cyberchase, which is about kids who use math to fight crime; my favorite childhood show.
I would watch things such as the Presidential debates with them, and participate in such debates with them, making them form an opinion that does not agree with my own. They would have to take all of the things I had taught them and think for themselves to quickly come up with a valid argument and informed opinion on the subject. Doing this would take them from knowing about the subject to truly knowing it and having their own informed opinion about it; thus thinking on their own.