MEDICAL STUDENTS/MEDICAL WANNABE STUDENTS!!!!

Try focusing on Biology, Chemistry and math. Maintain good scores and be knowledgeable in those three subjects. Those are the three suckers that'll keep haunting you for the rest of the time you'll be in med school, or so the people I know who went into medical field said so. Also try being knowledge-hungry about medical stuff, always helps knowing something about anything, even if its only a little. 

Don't get afraid when you see a lot of people going into the same and get demotivated when you see competition. It's a hard field to be in, not because the subject and course is hellish, but also because of how you'll be training to deal with humans beings who come to you for help and cure, and you can't mess up there, human lives a precious yes? Knew a teacher who would often taunt us brats back in classes about how you would spend half of your whole life just studying medicine and medical field, and even then you would still be learning even after being done with it. One of the things about STEM fields are that once you start studying and learning, it never ends. Even if you finish school, college and university you'll still learn and study more because it keeps evolving and changing everyday. 

But as I said earlier, don't let it all discourage you. If you have a passion for being in the medical field, and got a strong will, you will make it out and survive. Knew a lot of classmates who tried going into medical field just for the sake of "getting a good paying job" and got busted by the pressure and joined some easy technical field. You'll really need determination and sheer will to survive, not just brains and book smarts. It's easy to get down when someone brags or tells you not to go for it. But don't let that stop you from choosing what you want to be in the future. 

As for what you can do to learn more about the field, ask your teachers around if they're friendly, chances are they could drop some info or lore or interesting stuff that might be useful. Try finding someone who's in the med field and ask for their experience, could be useful. And of course the good ol' internet with gazillion load of info which can be useful (or not) if you know where to look for it. Doesn't hurt to research some for yourself, especially if you're being serious about going for it. 

P.S: I'm no med school student nor a professional or even amateur about the topic, but know too many people from my family who pursued med school and became surgeons, doctors and etc, so saying it from what they told me about it.