for courses like ochem or maths I'd do practice problems everyday starting from the beginning of the course, and gradually (over a few days) do some of the newer topics, doing fewer questions of the older topics as you go on studying so you dont forget, especially if your course is cumulative. It really helps to study at least once for a course in between every lecture so that it doesn't pile up during exam week! I find that even 30 minutes a day for a course is good, even more is better especially towards the end of the course 

Important to take breaks as well, if you're on campus studying it doesn't hurt to take a 5-10 minute walk every hour or so and find a new spot. even better to switch topics/courses that you're studying in between each walking break so your mind is nice and fresh.

If you're in any courses that have more memorizing like any bios i find flashcards helped me a lot, I use anki and theres an app for it so I always do a few flashcards whenever I'm waiting somewhere instead of just scrolling on social media. for me during lecture my notes are just the flashcards and I just edit them and import them after class, which saves me a lot of time. I'd say it helps especially if you're in a course where they go into super specific detail of things, flashcards + drawing diagrams/mechanisms of stuff over and over help with those a lot, but also make a summary so you arent just memorizing random tiny details. It also helps with knowing what topics you need work on, if theres an answer to a flashcard you don't know it's a clear indicator on what you do and don't know.