1) Skim through the contents page for that chapter and sub headers and have some basic questions, like what it means, how to do something, why is it important, categories for something.
Eg for my special dietary requirements subject, the main points are types of special dietary requirements , religious dietary requirements, what are my responsibilities as a chef for these customers and how we would prepare food safely for them to avoid killing them / making them sick. After that, I would read each part in detail. After reading a chapter, I would record myself saying a summary with some brief explanations in my own words within 5-10 minutes without looking at the text.
2) Record your lectures/lessons using your phone or a voice recorder and listen to it after class. I don’t catch everything in class so it helps me to fill in the gaps.
3) Make it interesting by reading/watching related content.
I’m a fantasy novel fan, so I think I need to read things with a story instead of just facts like a science subject. For example, for my biology elective about stem cells, I read articles about case studies and breakthroughs in stem cell research in other countries via magazines or newspaper articles, like how they use it to regrow different body parts. Or I watch documentaries about science stuff.
4) If you are an audio person, listening to relaxing background music may help to concentrate a bit longer like 15 minutes. I get distracted easily by noise so I can concentrate well as long as I’m listening to music in a quiet place.