Don't fetishize reading. Read because you enjoy what you're reading, you're getting something out of it, you would do it regardless of whether people will ever know. The rest of this list is about cultivating that internal motivation.
Find your level. Don't dive into the deep end when you haven't built up the tools yet. A comprehensive text book is likely not the way for a beginner to start. Alternatively, don't read something too easy for you. It won't be interesting if you're not actually encountering new ideas.
Avoid sensationalized science. A lot of things dubbed "popular science" try to sound cool but really miss both the significance of the findings they're trying to explain but also the mentality of a scientist. If an author is sensationalizing the science, making it sound more like fantasy/sci-fi, using buzz words, and treating any new result as if it's earth shattering, then they aren't focused and excited about the right things. Good nonfiction writers won't try to make something sound interesting by glossing over it with fantastical language. They will reveal how interesting something actually is by using as clear and intuitive language as possible. (Bad writers make basic things seem complicated. Good writers make complicated things seem basic.)
Look up words that you don't know. That's kind of the point right? You're trying to learn new ideas and approaches. Most key ideas should be defined in the thing you're reading, but sometimes there are words you just don't know. Maybe it's from the subject you're studying, but you haven't seen it yet. Maybe it's not tied to the subject, but still, you've never seen it. This is a chance to dig deeper. Look up the definition. Fit it into what the writer is saying. If you have time, the etymology (history of the word) can be extremely informative.
Reread. Sometimes you'll read something, and that won't be enough. Maybe there were things that were confusing. Maybe nothing was unclear in the moment, but looking back, you have no idea what the point of a chapter was. Don't think that just because you've read something means you should fully understand it. Give yourself time to go over tougher sections. Spend time on them.
Take notes. Annotate the text or keep a side notebook to write down definitions, insights, thoughts, questions, concerns, etc. This has two main upshots: First, while reading, it helps you digest what you're reading. You understand things differently when you do the extra cognition/analysis involved in writing something down. Second, you'll be able to look back on these notes in the future. Things might seem fresh now, but in ten years, it'd be ideal if you didn't have to read everything over again to remember what you thought. Your own personal notes will evoke your memories much better than any third-party synopsis.
Don't read multiple things at once. It is common for people new to reading to get over ambitious and try to read multiple things at once (setting something aside for days or weeks while reading other things). This is almost always that the person will give up on one of those things, or (more likely) that they already have but just don't realize it yet. Especially starting out (first handful or stories/books), read only one thing at a time. Let that story take you. If it's not interesting enough to finish before the next thing, then it's not interesting enough to finish full stop.Â
Frame your exploration in terms of questions not answers. One way to find things to read is to find things that reinforce how you already think about things (what answers have you already found). Alternatively, you could find things that help you ask new questions. What other ways can you think about your interests that you haven't even considered yet? This is not a question of reading those that disagree with you. This is about asking questions that you haven't even formulated answers for.
Reading is a skill, and like any skill, it needs to be developed. Don't fall into the trap of thinking reading is some binary (yes or no) attribute that you either have or you don't. Just like sailing, painting, woodworking, etc., the more you do it, the better you will be at it. You'll be able to pick up on more ideas, ask further questions, follow more intricate and nuanced details. And like any skill, there's no finish line. It's not something you should ever feel like you're "done" with. It's something to get better at forever.