I always find that by the time I get to the 4th or 5th I start to run out of ideas but then I force myself to gopast it and once I get to the 15th-20th the better stuff starts coming.
I used to do little mental exercises to help channel concepts like:
What if Charles Eames designed this?
What if it could only be made of wood?
What if it was designed 50 years ago?
What if I could do whatever I wanted?
What if someone asked me to make it as crazy as possible?
What if it looked like it came from the sea?
What if it was inspired by lobster shells?
The more random the better. It pushes you into a new space.
When I was at Evo Design we were doing some early work on a project called “Foot Pod” for the Explorer Group, a now defunct advanced design group. A lot of that work went to the Nike Innovation Kitchen and informed projects like Nike Free. Anyway, the key concept evolved from “What if it flexed like a metal watch band”… go back and look at the bottom of a Nike Free shoe and it bears resemblance to a the links in a watch band.