You've gotta approach this from an angle of highly supportive reasons why the school would be great coupled with the lack of an obsequious attitude. If I were on an adcom I would tire quickly of the "school is so amazing, it would be an honor to count my presence as an attendee here"
Do a little creative thinking, as said before, poke around their website. Does the school pride itself on supporting its students? Emphasize how important it is for students to have support during such a trying time as a medical education. Is it close to you geographically? Emphasize how important being close to family is for you. Does the school place a high value on treating diverse population? Talk about the things you gain from seeing diverse patients as a med student. There are ways to do this without sounding totally perfunctory/boring.
Generally, they are trying to assess how likely you are to go to their school if accepted. How much do you care about them? Some people will disagree with me, but having specific ties to the area (family, SO, etc.) are very compelling reasons for a school to interview you, especially if you're within the average range of stats there.
