Critical thinking means collecting absorbing important information and using that to form and support a decision or opinion of your own, rather than repeating or believing what you hear others say.
“Critical thinking skills don’t fully develop until adolescence, but the foundations for good thinking develop in younger children” and it is important to help children during the early stages of development.
Three Kinds of Thinkers
Critical Thinking for Children
You might also like Scott Berkun’s essay How to detect bullshit
Lifehackers How to train your mind to think critically