If I had to teach my younger self how to think, I think I would only focus on asking the same two questions over and over. They are very simple one-word questions, but they are immensely powerful at providing clarity. They are:
Why?
Really?
"Why" is about seeing the bigger picture, the context behind the current situation, and what is important. "Really" is about being more precise, as well as making sure you're not bullshitting yourself, by examining what you just said.
Here's one example, which will become repetitive but I hope the point will be conveyed. Let's say I feel like I need to go to the gym but don't want to. Alternatively, substitute "going to the gym" with anything you are forcing yourself to do, I just want to pick a concrete example here.
Why? It's important to spend effort on solving the real problem, so why do I feel the need to go to the gym? Because I want to get fit maybe.
Okay, it's hard to argue about the general direction of getting fit because physical health is obviously very nice, so now let's discuss specifics. Really? Do you really want to get fit, or do you do it because you've been shamed into caring about that?
Another way to take the really-question is: Really? Is going to the gym the only way to exercise? Clearly not. If you spend just a few minutes, you can imagine a plethora of ways of moving your body that are more fun and social than lifting weights in a gym: hiking with friends, any type of team sport, bouldering, silly dancing in your room, riding your bicycle on the weekend, doing your errands on foot, etc.
Of course, if you want to bulk up, going to the gym is probably the most direct path, but then again, why do you want to gain muscles? Is it for your own benefit? Or are you trying to impress others? In that case, why? Maybe there's a need to impress others because you feel like you're not very likeable otherwise, so you feel the need to be exceptional to be liked by others.
Really? Does the pursuit of superiority really make you likeable? Won't it just close you off from connection and make you desperate, or on the contrary, too judgemental?
So what other way is there to be liked by others? Or what if that is not the right question to ask? Why should it be about you being liked about others, as opposed to simply developing mutual relationships? Why are you so afraid of whether people like you or don't?
I could go on and on with this example, but you get the idea. The idea behind the two questions is to be curious about the problem, and let go of judgement as much as possible. Judgement is really the enemy of introspection. When you interact with thoughts like "I'm screwed up" or "No one likes me", it's basically guaranteed that you'll stop thinking clearly about your problem, because you're now stuck in a place of pain.
It is worth acknowledging that pain, because my god the world we live in can be cruel at times, for instance judging even very young children for not conforming to imposed standards, which are often completely arbitrary like in school, and then shaming them until they comply. There is real pain in how we get taught to relate to ourselves, and I do not wish to ignore that. On the other hand, that pain response rarely provides anything of value. I have never seen someone solve anything by flagellating themselves. And it is not fun to be around people who treat themselves that way either.
So perhaps an adjacent skill to asking good questions is the ability to see the disruptors of asking good questions, where being stuck in that pain mode is one example. Another example of a class of disruptors are the structures of power that surround us. A child in school cannot genuinely critique the school they're in, because the institution holds so much more power than the individual, especially a child. As such, they could never genuinely ask why it is that we have to go to school, because they'll be forced to go there anyway. And yet another example of a class of disruptors is the flow of distractions: entertainment, addictions, outrage, gossiping, sensationalism, blame, etc.
In the end, I would say that asking good questions is far more fundamental than having answers when it comes to being truly intelligent. You are always ignorant in some way, and how you navigate that ignorance is far more telling than all the answers you have accumulated. This is especially true when the source of most of the "answers" surrounding us is the technological system and the institutions that descend from it, because they all have their agendas. As Thomas Pynchon said:
If they can get you asking the wrong questions, they don't have to worry about answers.