Notice, Don't Think
The way to get startup ideas is not to try to think of startup ideas. It's to look for problems, preferably problems you have yourself. The verb matters: the best ideas are noticed, not thought up.
The very best startup ideas share three things: they're something the founders themselves want, that they themselves can build, and that few others realize are worth doing. Microsoft, Apple, Yahoo, Google, and Facebook all started this way.
Sitting down to 'brainstorm startup ideas' produces a specific kind of bad idea that sounds plausible but solves nothing anyone urgently needs. Real ideas grow out of lived friction.
“The way to get startup ideas is not to try to think of startup ideas.”
Key idea
Don't think up ideas. Notice problems, ideally your own. The best ideas are things founders want, can build, and that few others see as worth doing.