By watching every day life. I live in NYC, so the commute to work is material enough. People are crazy. You can really examine the ridiculousness of humans on the train. Like how someone fights over a bag brushing their back in a crowded rush hour train. Or the extreme PDA of teens licking the backs of their throats as the train lurches down the tracks.
Let's just say I don't have to look far to be inspired, even on a bad day.