JFX, I would first say that the tone of your post makes your aspiration seem like trying to plan for fortune in the future rather than happiness. But that is just my first impression. If you truly do have an interest in anesthesiology, and/or you have exposure to the medical field already, then it isn't a terrible idea to think about what you need to do for the future. Coming straight out of high school into medical school (a 6-year program... only a few out there left, and mine is likely to be extended to 7), it was important for me to perform well in high school. This includes ACT/SAT (whatever your region normally takes), grades, extracurricular activities and leadership posts held. If nothing else, this will help you get into a better undergrad college and enhance your chances at landing a spot in the very competitive world of getting into medical school later. Also shadowing, as jocwyo mentioned above, would be great to first give you an idea of whether you wanted to pursue a career in medicine (at least anesthesia anyway), and also serve as proof to potential med schools in the future that you're dedicated to the idea of becoming a physician.
But your main focus at this point should be figuring out what in life makes you happy. Just try to do well in school, leaving as many opportunities open to yourself as you can, for whatever you choose to do in the future.