The ALA RUSA award-winning classic and very instructive article for those interested in doing a good reference interview is online. Also note the full-text of the annual winners from 1986 to date are linked in the left sidebar.
Oranges and Peaches: Understanding Communication Accidents in the Reference Interview . From a discussion on learning the reference interview at LIBREF-L .
Also of note: Infopeople has put its Reference Interview Skills workshop materials  online.