I actually called every school that I thought I might be interested in applying to, and several were willing to discuss my application with me and make suggestions about what I could do to strengthen it. It took a lot of time, but I got several good tips, and so I recommend doing this if you are wondering whether you are competitive for a given school. I was told by several schools that not only do they want me to have volunteering experience, but it should be medical volunteering, and it should be recent. So, even though I already have non-medical volunteering that I have been doing for years, and I am a (volunteer!) co-investigator for a clinical trial, I also started volunteering in the surgical waiting area of one of the local hospitals. Although, I have to say that the hospital volunteering seems to matter more to the state schools. The more research-intensive schools that I talked to were more interested in hearing about the clinical trial.