It’s the huge question, before they head off to college. The answer is do what you want. Experiment. Don’t pick something because you’ll make a lot of money. Do pick something that you love and would be happy to do every day for the rest of your life. That thing can change, as we evolve, but we all have callings, a path. Think about what you really love, have the intention of finding out what your career should be; the universe will reveal the path. If you keep changing your career, don’t think you wasted time or made a mistake studying something. There are no mistakes, you were meant to learn it, it will have use for you in life. Just trust in the universe and be aware of your surroundings. Listen to any messages that are sent to you. Above all listen to your heart, not your mind. Take your time, let it be, don’t let anyone push you into something you don’t want. 

Good luck on your journey! :D Namaste!