it's probably a 50/50 thing these days. The cream of the crop (35 MCAT's/3.8 etc) goes in the first round of apps. The smart average folks get in as well the first time around or get waitlisted because they chose schools that they could get into. Dumb average folks, like me, get waitlisted at our schools that are reaches and go at it again the next year.
Things that help:
-Shadowing a doc to make sure that your heart is in the field and it is definitely what you want to do with your life
-Rock the MCAT
-Take a year off to work in research/clinical and HAVE SOME FUN before committing your life to medicine
-Take classes you enjoy and can do well in
-Take post bac courses that you enjoy
-Talk to physicians whenever you can to make sure that you have NO question that being a doc is your passion in life
-Know yourself before applying
-Save up some cash cause it is not a cheap thing to apply
-relax about the whole process, because if you REALLY want to be a doctor you will make it happen