I am also a student going into high school next year. This means I can relate to students on a much deeper level because I understand what school today is like. I have been on Honor roll my entire life and I am going into Wooster's International Baccalaureate (IB) program next year. I have been helping my peers with English for about 5 years and have been pretty sucessful.
I liked how personal they made the material so that I liked it
I typically start with material they are currently working on in class to get a sense of their workload. Then, I ask them what they enjoy doing in class and what they need more help with. I then start planning on how to incorporate the things they love and the things they don't to help them get better at the subject they need help in while still maintaining fluency in the things they're already good at.