That's a great question! The study skills you develop now will stick with you as you make the transition into college and beyond. What always worked best for me personally was making study guides and just in general being as organized as possible. It can be hard to keep everything straight when you have multiple classes with different deadlines. Using an organizer and/or calendar will help with this.
You can use the calendar to plan out when you need to start studying for an exam in order to avoid "cramming." For example, if you have an exam on April 1, you can mark on the calendar what day you want to start studying (try 1 week in advance to start). That way you can say on the Monday before the exam, I will study Chapters 1-3, then on Tuesday 2-4, and so on.