Last week I played the downloadable demo for Etrian Odyssey 2 Untold: The Fafnir Knight, the latest in a great series of dungeon-crawlers for the 3DS. It struck me as an example of a particularly good demo, one that made me very interested in playing the full game.

We don't get a lot of game demos these days, because they can take too much time from actual game development and, if the demo or game isn't very good, can actually lower sales. Still, quality demos can help raise a game's profile and improve sales, especially for niche games or new franchises. Here are five things that all game demos should copy from Etrian Odyssey's demo.