How/when did you make the decision that med school was the route for you? (In my case, 99% dental school, but same thing.) At the beginning of last summer.
How did I make the decision? I thought about what I wanted and what I got a kick out of a LOT, then tried my hand at volunteering, and read everything I could. That included reading every remotely related thread on this site.
Is it something that you just felt your "gut" told you to do? Yes, then I volunteered, and loved it.
Locked into a career you didn't like were sick of? I never knew what my career path was, and became sick of not knowing. Fortunately, my "career" was "on hold" (cough, contract ended at my job and was let go, cough) at a convenient time, so I spent many a day last summer trying to figure out just what the heck I was gonna do next.
Didn't know what else to do? Partially. One thing I did know was that I did not want to work in a cubicle for the rest of my life. (What's humiliating is that right now, I have to work in 3/8 of a cubicle to pay the bills. It strengthens my desire evvvvvvery day.) Anyway, once those cubicle jobs were eliminated, I thought about my options and what I wanted from a job, and went dental. If only I had done this at age 16!
Some event spurred you on? On a total fluke, I wound up working for a dentist at the end of my college days. I later realized that the experience was far better than anything I'd studied in college or experienced in any other internships/jobs, of which I had some pretty diverse experiences. Oh, and the future event of being unhappy for the rest of my life with my job was definately a motivating factor.
Religious reasons? Nope. I could see myself doing the occasional medical mission right now, but I don't think it would be linked to any religious group in particular.
Because you're smart? Nah, though others and all those damn standardized tests they make you take in public school have confirmed that I am, I guess. I've learned that drive is rewarded so much more than intelligence in the medical world. Throughout life I've known I've had drive and intelligence, but they were just expressed in the wrong opportunities, for various reasons.
I tried to keep it short. HTH.