People always ask me how I capture the moments I do, and my only real answer is this:  
I'm an experienced people-watcher. 

You figure out the flow and timing of the crowd. 
You listen for laughter, the excitement in someone's voice as they lead up to the punch.
You learn to keep your ears open, even as you're capturing a different moment. 
You notice the small details. You look at everything. 

You learn. And you keep watching.