The main this is USMLE scores. However, if you don't have the best scores...other things can contribute, especially LORs and depending what specialty, extracurriculars/research. Publications are helpful. Med school grades not so much because you might be in a completely different system that the US does not use and so therefore will not understand. Class rank may help, but again this isn't a definite. Although what mmed said above may happen...I don't think it'd be usual. As an IMG, they know that you may have less of a choice compared to a US graduate, so they may be more likely to think that you're not using them as a backup. So generally, when you apply for the Match...just apply to a wide group of programs with a lot of variety in the types of programs.