While you are in high school, try to get work in a hospital, doctor's office, or laboratory. Perhaps you can get an internship, some of which are paid, in one of these settings.
B.S./M.D. programs are looking for students who are very strong academically but also dedicated to a career in medicine. Many programs have minimum academic requirements to even be considered, and this typically includes being in the top 10% of your high school class.
B.S./M.D. programs allow seniors in high school to apply to college and medical school right from high school. There are about 80 of these programs throughout the United States.
As one of the world's fastest-growing populations, people aged 65 and older require unique medical and social services, and a vast array of industries cater to them.
The short answer is . . . as soon as possible! Medical schools often want to see evidence of a busy life and community contributions from as far back as the age of 16.
This site deals primarily with undergraduate programs, so if you're interested in applying to medical school I'd recommend that you start by looking into the AMA, the American Medical Association.
There are three particular health specialties for which there will be an increasing need in the coming years.
Today, the role of genetics in medicine, basic research, biotechnology and pharmaceutical research, forensics, agriculture, and animal biology is growing by leaps and bounds.