Some beginning books:
"Philosophy: The Pursuit of Wisdom," Louis J. Pojman;
"Ethics: Discovering Right and Wrong," Pojman;
"Classics of Philosophy," Pojman;
"Philosophy for Dummies," Tom Morris;
"The Slightest Philosophy," Quee Nelson;
"Nihilism: The Root of the Revolution of the Modern Age," Eugene Rose;
"Plato and a Platypus Walk into a Bar," Klein and Cathcart;
"A Philosophy of Universality," Aivanhov;
"Intellectuals," Paul Johnson;
"The Philosophers: Their Lives and the Nature of Their Thought," Scharfstein;
"Return to the One: Plotinus's Guide to God-Realization," Hines;
"One Magisterium: How Nature Knows through Us," Nuallain.
"Critical thinking" is reasonable iff it is constructive critical thinking. There are many non-constructive attempts at genuine critical thinking.
A classic written well before modern "critical thinking:"
"Human, All Too Human," Nietzsche;
"Critical thinking" is/was a buzzword for "thinking" as such had noticeably declined in American youth. It basically imports rational analysis, with a flavoring of 1990s mass-libness: [ Wikipedia.org Link ]
If you are an American, you should start with "fixation of belief,' by C. S. Peirce. Then move on the elaboration by William James called "Pragmatism."
DO NOT start with the frickin' Greeks! They might as well be speaking Martian! You have to start a conversation with someone who is comprehensible to you.
After James, read "Prolegomena to any future metaphysic" by Immanuel Kant.
From this jump-off point, you should be able to find your way, carefully avoiding Rand (at least).
I do not agree that critical thinking is best accomplished via studying philosophy...at least not the mainstream philosophy that seems to be practiced in in the US.
Well the obvious answer is to take courses in college. But other than that, I'd recommend starting with Socrates, particularly the Apology. Then, perhaps find and read a collection of the 100 greatest philosophers, there is such a book, which captures their main ideas. Then, read further into whatever areas interest you. Critical thinking is Epistemology, a sub-branch of philosophy. For that, start with Descartes.
Open your eyes and mind. Look up, look around, start to think for yourself, and most importantly of all avoid the philosophologists
You begin by taking courses in the subject. How you may 'do well' at it will be determined by how you apply critical thinking by using your Brain.
After years and years of studying, you will eventually acquire your PhD in Philosophy.
So......now.....what are you going too do with it?
Start by reading books critical of philosophy.
go to YouTube and type "Justice with Michael Sandel episode 1"
withought the quotes, pay attention to the video.
he has 6 or 7 other episodes. He is a Philosopher, Author, and Professor at Harvard.
The video's are sessions at Harvard. Really inisghtful!
Scripture is dead. God is Living and active.
Gaze at the stars. Ponder infinity. Contemplate the Sun. See how everything intertwines and connects. Become aware of your thoughts and the unconscious processes going on behind each thought. Look for similarities in others rather than differences.
Ask yourself what fundamentally exists until you reach the ontological first. The Absolute.
Ask yourself earnestly.. who am I? What am I?
well, along with reading a lot. You could see if there are groups of amateur philosphers that meet up live to discuss things, It is possible they do something like Journal club, where everybody reads a particular article before getting together to discuss it. I think has get togethers of philosophers live, so you could meet with them and discuss things. Click the link! [ Meetup.com Link ]
Reads some books. Discernment. Instinct for things beyond yourself.
Start by reading philosophy books.