What you need to know about this photograph...

While attending a birthday party of a good friend I noticed a couple of kids playing under the dining room table. The light coming in through the nearby window was big and soft. You can see the light from the window lighting her left cheek, camera right. The light on her right cheek, camera left, was reflecting off the white cushion on the dining room chair next to her. While she was under the table she was near the end closest to me and the window just behind me and to my right. I hope that is not too confusing.
While she is as cute as can be, it was how the light was lighting her adorable face that captured my attention and made me press the shutter. It was the moment she noticed me that I took the photo. Her curiosity shows in her beautiful eyes.
If you find yourself at a family event with kids scrambling around. Place yourself near a big window, camera in hand lens cap off, and wait for a child to walk into the beautiful window light. Also, because children are generally on the move, take a lot of pictures to increase your odds of capturing the perfect moment.
I shot this image with my Canon 135mm lens at f/3.2. This created the shallow depth of field and the wonderful bokeh behind her. If this photo were taken with a much narrower aperture you potentially would have been distracted by objects in the background. I prefer to always keep the attention on my subject, especially their eyes. If you are familiar with my photography you know that the who is more important than the where.
Here are the tech specs of the shot: Lens 135mm f/2.0 L series lens, shot at f/3.2, 1/100 sec, at ISO 400.