Metacognition is simply thinking about ones own thought process. It can be somewhat challenging at first, but is an important skill to build because it cuts out the "clutter" of emotion, preconceptions, and bias and allows the critical thinker to recognize those barriers of thoughts in others. Metacognition requires practice and the ability to admit to ones own short-comings and obstacles that prevent sound critical thinking. Metacognition is a vital aspect of every level of education and should be considered for inclusion in any essay about critical thinking.
In order to think critically, one needs a level of skepticism to not only question their own thoughts and beliefs but to also question the ideas and information of others. At the same time, this skepticism should not move into cynicism, which prevents open-mindedness and the ability to appreciate the ideas and thoughts of others. As with many aspects of critical thinking, it's a matter of balance and practice. Writing about critical thinking is one of the best ways to recognize and practice this balance.
Similar to skepticism without cynicism, critical thinking requires optimism in order to ask relevant questions and consider the information provided from a variety of perspectives. In this regard, critical thinking also involves empathy. As with other balanced aspects of critical thinking, optimism shouldn't slip into naivete or blindly trusting provided information without question. One must balance the attitude that the information is correct with the possibility that it is not. To keep an essay balanced, references to optimism without naivete should be paired with ideas of skepticism without cynicism.
Socrates was the Greek philosopher who began a method of learning that involved asking a question, listening to the answer, and then asking another question in response to that answer. The Socratic approach to critical thinking is a powerful tool. The method can keep the critical thinking process moving forward so that sound ideas and conclusions can be developed. Like many other aspects of critical thinking, it takes practice, but can pay huge dividends on the way to clear critical thinking. This practice lends itself particularly well to the structure of an essay and is essential to critical thinking.