Prioritize your commitments at the beginning of a week. (School, work, social life, extra curricular activities) Be honest and be ready to sacrifice things that you enjoy over things that need to be done. Once you know the order break things done into steps and timelines.
Use the time when you are most motivated for the most important tasks. School work should be used for those times because you have the most control over it.
getting to work
Get organized and have a plan before beginning something. Stay focused on the most important task. Ask yourself these questions: What do I want to accomplish? What do I need to get things accomplished? Am I being honest with myself when prioritizing? (need VS wants) The decisions you make will impact others. Ask yourself challenging questions. Example: What happens if I don't get my assignment done? I need to tell my friend that I cannot go out tonight because I need to work on it. How do I do that? I don't want them to be angry.
Be proactive and talk to the people that are impacted by the plan. School -> teachers, parents Work -> employer, parents Social life/extra curricular activities -> parents, coaches, friends Ask questions to gain clarity and get your needs met. The more people know what is going on in your life the better. It will save time when you need help.
Think thoroughly before making a commitment. Leave time for yourself. Be honest with what you need by setting boundaries. Resolve conflicts. Have "point people" accessible to you.