When you put your subject in a frame, you are saying, "Look at this." The focus you choose for a photograph is the same. You are directing the viewer's eyes to your subject. But what if what you want to focus on isn't what your camera sees as the subject?
In the photo above, I used the camera's automatic focus mode. The camera looked for the closest thing to the lens with detail and focused on it. In the top photo, I manually chose the focus point for the camera ... to zero in on the child's face, instead of the arrow on the sign that the camera liked.
Focus is very important for capturing those catchlights that you've been noticing too.
Here, I put Sophia in a place where her beautiful eyes would be lit up by the window light, but the camera's automatic focus chose her hair as the subject.
In the photo above, I changed focusing modes to manual selection and used a focus point on her left eye.
If you don't know how to change focusing modes on your camera, look up a tutorial online. For my camera, I searched, "canon 7D focus modes." When I did this, I found my camera had several other focus modes I didn't know about. I'm excited to try them. (About the tutorials: I found this one and this one useful.)
I'm also excited to see your photos in the Familiar Light: Try It Flickr group. I'd love to see how it goes for you when you try it: choose your focus.