1) Get into a good medical school. Allopathic and located in the United States = will max your chances.
2) Do well on the Step I, i.e. > 230. Which means that you need to pay attention the 1st two years of medical school.
3) Do well on your clinical rotation ( 3rd / 4th year). esp on your Ortho rotations, Surgery and Medicine blocks. You should honor all of your Ortho rotations.
4) Find a mentor early on in medical school and do either research projects or shadow them. Make sure that Ortho is really what you want to do.
5) Get strong letters of Recs from your dept and if you can, one from an away institution.
6.) If you do well on #2+3, then you should be in the top 1/4 of your class and may make AOA, which would help your app alot.
7.) Have a life! Don't just hit the books all day. Most people in the field of Ortho have something else on their apps other than numbers. ie Sports, hobbies, other professions before med school, etc.
8) If you get interviews, be prepared for them. Be smart about where you rotate, because majority of the people will match either at their home program or the places that they rotated.
** Almost all Orthopedic programs in the U.S. get ~100-150 apps per spot because the applicants use the shotgun approach when comes to applying. To secure your self a spot, you really need to work hard. Having a little luck in the match process will also help. **
Those are my advice, take it for what it is = just my opinon. Hope this helps, good luck.