Look for opportunities to use measurements to help your judgment. And also work on developing good judgment (about anything) and developing ways to prevent, detect and correct bias, dishonesty and irrationality.
How? Many ways. E.g. these articles could help:
Let's talk about a different way.
Assuming you're an adult, there are some things you're already good at judging. There are some areas where you're confident, competent, skilled, etc.
You can find more stuff which is similar or related and work on that. You can try to expand the good judgment you already have by applying it to more things.
Suppose you learn math to pass school tests. You might later find the math you already know is also useful for figuring out whether a system of pulleys will let you lift a large stone. And then later you you find the math you already know can help you analyze video game strategies, e.g. figuring out how much damage you can do in 60 seconds by casting different sequences of spells.
Skills often help with many things that weren't the original purpose you learned them for.
So you can take skills you already have and look for more stuff they can already help with. If the skill is related to judgment, and you find more ways to use it, then you're expanding the scope of what you can skillfully judge.
You can also expand on the skills as you apply them to more areas. E.g. you might find learning a few more mathematical techniques helps you with your pulleys or video games. Similarly, you could learn a few new things to help your judgment skills deal with new areas.