A short overview of paper prototyping, in theory and practice, from 1994. Full of insights. Reading through this makes it clear to me that using Keynote as a prototyping tool is really much closer to paper prototyping in spirit than to the software prototypes he compares them against.
“Construct models, not illustrations.” (p1)
“[With a paper prototype] interface designers spend 95% of their time thinking about the design and only 5% thinking about the mechanics of the tool. Software-based tools, no matter how well executed, reverse this ratio.” (p2)
“Spend enough time crafting something and you are likely to fall in love with it. Knowing this, team members may feel reluctant to suggest that their colleague should make drastic changes to the lovely looking, weeks-in-the-making software prototype. They would be less hesitant to suggest redrawing a sketch that took an hour to create.” (p3)
“… no matter how hard you think about it, you aren’t going to start getting it right until you put something in front of actual users and start refining your idea based on their experience with your design.” (p5)
“It can be terribly difficult to keep still while the user spends 10 minutes using all the wrong controls for all the wrong reasons. You will feel a compelling urge to explain the design to your users. Don’t give in.” (p9)