http://www.gamasutra.com/view/feature/6100/a_journey_across_the_main_stream_.php So the above article discusses some assumptions and interface decisions made during the initial development of the first Season of Sam 'n Max, from TellTale Games. If you haven't played the game, you still might find this article interesting. The game designer sits his mother-in-law in front of his game and basically runs her through an alpha test of the tutorial and highlights how someone who is a non-gamer first encounters a game like an adventure game. His mother-in-law reacted very similarly to some other non-gamers I've encountered trying to play a game before as well. I found this very interesting.
It also has some good interface design advice, for those of you interested in that area like I am.