Step 1: Observe
Before new ideas can be explored, it is important to study the weaknesses of current designs. In most cases, start by asking experienced people about their own observations with a device. What are the current design's shortcomings? What parts of the designs are most likely to break? What features of the current design do you they the most important? A similar line of questioning should also be asked to yourself after each prototype is made. Observing the way current designs work is the springboard off which to conceive new ideas.
Look carefully at the simple tools around you and you are sure to find dozens of subtle design choices that make them more effiecient and intuitive to use. Notice the little ridge on the "J" key to allow the user to re-center their fingers without needing to look down at the keyboard.