What i find really helpful when studying is finding something interesting in your study material and focusing on that. by focusing on the interesting things, it also helps to relate the topic to things you already know, which helps memory.
it also helps to be aware of things you need to know and details you dont; like if you need to study history and the teacher is testing you on what happens but not the dates, you could focus on the events and possibly ignore the numbers. to skim or not to skim, in a way.
writing down your notes with pen or pencil is also a great memory tool, i find the action of writing works better for memory than typing. plus, you can also draw symbols or doodles of the topic to help you :D
some cool strategies i use now for note taking are mind maps instead of normal, whats-on-the-board, notes during lectures or instruction. if you're studying text documents, i suggest annotation (in the margins) and highlighting if you can; if you can't highlight/annotate on the book, you can also extract quotes from the passage and put them into a separate document to comment on--this is notably helpful for very challenging texts. if you're just reading the text book and they're going to go over it again in class then you can just chill out imo and read leisurely.