Little things: a man waiting for a tow truck on the side of the road; a teenager juggling projects, driving tests, and prom plans all in one weekend; a line stretching around the block in front of a movie theater on opening weekend. Big things: the fight for gay rights; the imbalance between the 1% and the 99%; the news that leaps off the front page or the computer screen, sometimes in real time. There is so much to draw on, and it doesn't have to be a big climactic moment at all. A teacher once told me there is drama in brushing your teeth, if you approach it in the right way. Learning to open our eyes and ears (and noses and all the rest) to the small stuff is all part of world building. I want my characters to walk through a concrete universe full of the results of others' actions, surrounded by the people who make that world what it is, reacting to their world as if they are physically breathing it in and out of their bodies. The question of detail may mean the difference between a story that tugs fitfully at your trouser leg and a story that grips you by both shoulders and stares you point blank in the eye.
Another little beauty is that detail work can make character building easy, because the world is an active participant in who that person is or isn't, who he or she becomes. Noticing what my characters notice has been very instructive.
Random writing exercise: Take a character you've written or are thinking about... and change the gender, just for a day. Rewrite scenes, write new scenes, introduce this character to their other-gender self over coffee. Make your character genderless, if you want. Discover how much this changes your perception of your character. Get to know your character better.