Keep on top of your schoolwork and homework. Make sure to revise and ideally study most days, and make sure you understand everything. If you don't understand something, try watching some videos online, or ask your teacher.
Make mind maps, or summarise your notes in the way you find works best. This really helps because not only are you making it easier for you to study later on, you are already studying as you have to understand the topic, and be able to put it into your own words. Hope this helps :)