Freedom offers some advice about how to stay focused when studying:
Studying is tough. Whether you’re a veteran student getting a Ph.D. or someone starting high school, figuring out how to stay focused while studying is a challenge that we all face. Whether your biggest challenge is social media, procrastination, time management, or a combination of all three, we’ve got a variety of tools and techniques that can help minimize the stress of studying and keep you focused on what matters.
Ultimately, there’s no quick, one-size-fits-all solution to staying focused while studying. Different methods and tools will work better for some than others. However, with a little trial and error and the tools and techniques above, you can create a routine of focused studying that works best for you.
The individual techniques Freedom suggests are good. But the final point about being mindful of and doing what works for you is really the trump card. If something doesn’t help, don’t do it simply because it’s on some list of suggestions. On the other hand, if you find something different that you do find useful, by all means, make that a core part of your study routine.
On the importance of focused attention, see also this post.