Keep all of your notes together. A folder is great for this especially a ringbinder because it is easier to see all your notes at once and flip through them.
Get a planner or a diary. To keep track of your assignments and due dates. You can also put personal events in here. This will help you plan your time wisely and prioritise important tasks.
Plan out your day. I do this on a separate piece of paper from my planner. This is great for working out exactly what you need to do. You can make this into a timetable or just list the tasks.
Keep on top of homework and assignments. Try not to procrastinate and get them done as soon as possible when you get them.
Pack your bag and plan your outfit/uniform the night before school. This will stop you forgetting things in the morning rush and means that you can have a few extra minutes in bed!
Make revision notes throughout the year. Not only does this help consolidate your knowledge, it also means that you will have all the notes you need for exams/finals.
Use your time wise but also have fun. Work hard and playhard but please remember to rest!
Keep a list of your goals. These can be longterm or shorterm but they will help keep you motivated and remind you what you are working towards!