Tips on the Prevention of Social Engineering?

SecGuy asks: "I'm constantly bombarded with news about gee-whiz security technology aimed at protecting the "front door" of an organization. Yet social engineering -- and, more broadly, human failures of various kinds -- lead to a large percentage of successful hacks. I'm curious about what systematic approaches (if any) have been successful at building up an organizational immunity towards social engineering attacks and generally reducing the types of human failure that lead to security compromises. A lot of approaches I've seen boil down to hectoring and punishing, which (a) doesn't seem to work well, and (b) generally pisses people off."