Talking with other theater designers lately - looking for a handle on their design problems - and grappling with starting a few problems of my own... made clearer to me this one fact of design -
The seed of a solution is within the problem itself.
A perfect example: one young designer needs to design a prop "machine." Doesn't much matter what this machine does as long as it looks cool and generates stage "business." Well! That's not much to start from in generating ideas. In talking about the play, however, we realized this show was set pre-electricity. So flashing colored lights were out. But... How about approaching the machine in a steampunk way? Design it to accomplish some modern goal, but with old fashioned - in this case candlelight - technology. Sudden excitement! Ideas!
The seed of a solution.