Whenever I want to start something, I always keep it on paper. Having something tangible that you can access anytime and everywhere keeps your ideas from falling out. Doodling's awesome, and it helps organize your thoughts better.
I often carry a small pocket notebook and a pen in case I have a wicked idea anywhere. It helps a lot.
A sketchbook's not bad either, if you're staying home most of the time.
When I'm at home I'm probably to bored to come up with ideas.