My most frequent story starter...is a vague concept of a conflict. A broad view that's mushy and loosely defined. It often is rooted in emotion; be it restlessness, resentment, retribution, or reconciliation. There's usually some sort of injustice at the core (in today's real world, how can you escape it, right?).
From there it moves to character. Who is feeling these things? Who is most impacted by the situation? Who is in a position to affect change? Who stands to lose the most? Gain the most? Be damned either way, but die if nothing changes?
Then Why has to be answered.
Then Why Now.
Then With Whom.
Then Despite Whom.
Then What Magic.
Then...then I have a concept that kicks off an outline around a conflict that builds a complex plot for complicated characters.