I graduated last year.

Can't give you specific advice on the pre-med ways, since in Europe we generally get into medical school when we're 18 and the course lasts for 6 years instead of the 4 in the US.

Exercise. Eat well. Stay healthy. This will seem all too obvious and hence easy to ignore until you're in the shitter, so make it a habit while things are still great.

If pre-med is anything like med school it's 100% about discipline and dedication.
Don't pull all nighters. The sheer number of hours you can sit down completely focused every single day will make it or break it.
Consistently work harder than everyone else, that's the deciding factor and it all boils down to it. Unfortunately there's no magic formula other than that.