You're not going to be good at it, at first. It probably takes a good 6-12 months to do it all correctly and most developers don't actually learn how to do it all properly.

But here's my cheatsheet if you actually want to spend the time to get really good at code review. Save this comment so you can keep coming back to it.

First, you need to relearn the programming side, making code in a specific way that has the capacity to be reviewed correctly. Don't think about code made to accomplish a goal because you should already be able to do that. Instead make sure you understand what makes code easy to review by someone else.

Why: You may have been stuck in an environment where someone else was either fixing your mistakes for you (depriving you of your opportunity to get better at writing reviewable code), or you may have been in an environment where you were getting the wrong feedback.

How: Read this link: https://mtlynch.io/code-review-love, then read it again next week, and again the following week. Once you intuitively can make reviewable code, it'll be easier for you to teach others how to make reviewable code (which makes your reviews easier to perform correctly).

Second: Learn how to actually give feedback in a way that gets things fixed.

How: Read this: https://mtlynch.io/human-code-reviews-1/.

Third: Don't try to write or correct documentation before you understand the "Grand unified theory of documentation" Link: https://docs.divio.com/documentation-system/. TL;DR: Most programmers don't understand that there's actually four different types of documentation and assume that the kind that they right is what's actually needed.

That goes into technical writing, which is another skill you need to develop but makes projects better as a whole, which makes it easier to review code.

Fourth (bonus reading material): antirez (the guy who made redis) went through his whole project and did a kind of census/retrospective on all the comments inside. It sort of accidentally turned into a good practical advisory on writing comments that actually mean something. Link here: https://antirez.com/news/124