1. Develop a routine. Listen, we all have those days in which you'd forget your head if it wasn't attached. If you have a routine built in, you can use that "auto pilot" to help you get prepared. Small things like going to your locker at scheduled times throughout the day can make sure you have the right books to class. Establish a time to write down homework in your planner or calendar and ALWAYS write in it (even if you wrote "NO HOMEWORK!!!!!) 

2. Have a calendar, and use it!! If it's a calendar in your phone often times you can color code items and set reminders as well. Written calendars are often visually easier to see that next month is that big Trig final to study for right after a Spanish vocabulary test. This will help you manage time better. Also, it teaches you how to assume responsibility for yourself. Use your clocks and timer's too. If you have a lot of homework, use a timer or clock to manage time and help you take breaks. Sometimes I used to get caught up learning about something off task in science then I skipped language. If you consistently look at the time, this can easily help redirect you. 

3. Develop a list of tasks to complete. This will help you prioritize homework. Start with the most difficult while you are fresh and energetic. If you don't get to the small stuff, bring that with you to class and complete if you have down time. This was how I managed time since I spent my evenings in after school activities. 

4. Make a finished project file. Keep your assignments, but not in a backpack or locker where they can add to messes. Keep a file by subject and grade. If you need to look back at files for examples of work for college or to help you out it will take less time to find. This helps with notes too. I kept my geometry notes for years. It ended up helping me as I taught high school later.