First, you need to look at the subjects that you like most and you are comfortable with. Then, choose the ones that you think will help you achieve your goals and also in your career. Contacting a career expert in your school may also be of help in helping you choose good subjects.
Look at what you want to do in life. Choose something that will help you with that goal. (If you don't know what you wanna do, look at your best skills that you are most proud of, and find a way to incorporate them into a career, then pursue that