The same is true of other concepts in basic logic. If you think about them and use them, then you’ll feel comfortable with them and recognize certain argumentative strategies and techniques in anything you read without really trying. The precise terminology will follow along on its own. If you are interested in practice, one good place to find help is this site’s forum. There you will have a chance to read lots of arguments and see many of the techniques described on this site put into practice. You can also ask questions about the validity or soundness of particular arguments — there are plenty of people who can help you to understand better where an argument goes wrong or gets things right.
Critical thinking of any kind is never universal in any individual; everyone is subject to episodes of undisciplined or irrational thought. Its quality is therefore typically a matter of degree and dependent on, among other things, the quality and depth of experience in a given domain of thinking or with respect to a particular class of questions. No one is a critical thinker through-and-through, but only to such-and-such a degree, with such-and-such insights and blind spots, subject to such-and-such tendencies towards self-delusion. For this reason, the development of critical thinking skills and dispositions is a life-long endeavor.