Chemistry or biochemistry = pretty good .
Math, applied math, statistics would be great as a minor.
They’re looking for many sorts of experience. PCT is a way to get paid work in hospitals, but volunteering and shadowing are also expected.
Being premed is so difficult because you have to juggle so many things and be excellent at them all.
The best way to prepare is to become very efficient at studying and learning; going for mastery not just basic understanding; improving your time management skills; asking your teachers for help, extra work, etc. (because in college office hours can be the difference between a B+ and an A-.)