As my friends know, I like to shoot people in the crowd at public events. But sometimes it is so packed that it's almost impossible to do. You could park yourself on a corner to shoot people coming towards you but even that may not work if you can;t get a long enough view.
There is another way to go about it. Sometimes I will walk through a crowd with the camera at my hip, finger on the shutter button. If I see something interesting I point the camera in the general direction, click and hope for the best. Almost no one notices. Surprising how often I get a good result.