When you have trouble with things—whether it's figuring out whether to push or pull a door or the arbitrary vagaries of the modern computer and electronics industries—it's not your fault. Don't blame yourself: blame the designer.

So what does a good teacher do? Create tension - but just the right amount.

In my opinion, no single design is apt to be optimal for everyone.

A challenge to the designers of the world: Make signs unnecessary.

In the university, professors make up artificial problems. In the real world, the problems do not come in nice, neat packages. They have to be discovered.

The world is complex, and so too must be the activities that we perform. But that doesn't mean that we must live in continual frustration. No. The whole point of human-centered design is to tame complexity, to turn what would appear to be a complicated tool into one that fits the task, that is understandable, usable, enjoyable.

No product is an island. A product is more than the product. It is a cohesive, integrated set of experiences. Think through all of the stages of a product or service - from initial intentions through final reflections, from first usage to help, service, and maintenance. Make them all work together seamlessly. That's systems thinking.