I'm bringing this up because I'm the ward choir director and :
-an extra practice 20 min before the ward party was hijacked by all the missionaries, elders AND sisters, who showed up for 2 min and then left to go greet [random investigators] showing up early. Since they make up over half the choir (big city ward so 4 sisters and 4 brothers), we couldn't practice at all, wasting me and other member's time.

-last Sunday one pair of elders (most of my bass section) scheduled appointments immediately after choir practice, so they had to skip practice to eat lunch.
They obviously don't realize that working with the members is only possible if they don't behave like jerks (and they don't realize that singing in the choir is the highest form of service in the church).
All this venting to propose (to all you GAs reading this) that the MTC give missionaries-in-training basic social skills, so the members don't become as annoyed as most non-members by them. Do you have other examples? While we wait for social training 101 to become a chapter of Preach my Gospel, what can we (those of us on this board who still have some contact with the missionaries in our wards) do about it? I already tried to scold them on Sunday, and candidly explain why it was not OK to do that, but it's hard for me because I'm about their age, haven't had much practice scolding people, and they used the "missionary work comes first" trump card.