Getting into residency is hard. Understanding how to rank programs for the Match is easy. Thanks to a Nobel Prize winning economist and his colleagues, the current Match algorithm ensures that your desires are the priority over the residency programs’. What this means practically is that you should rank your first choice first, your second second, etc. There is no need to try to play the system.
I’ve had applicants tell me that they plan to rank a less preferred institution higher because that program has more residency slots. That’s a huge no-no. The applicant will actually be harming him/herself with that strategy!