One easy way to bring more focus and attention to your subject is to blur the background.
A smaller f-stop number will result in sharp foreground images against a blurry background. You can use this technique to bring more attention to subjects such as children and pets. Subjects in clear focus will generally pop off your photos when filmed against a blurred background.
A larger f-stop will produce a larger depth of field, meaning that a larger area of your photo will remain clearly in focus. This technique would be most used by landscape photographers, who often want everything between their camera and the horizon in clear focus.
In the photo below, May Blossoms, you can see how the blurry background actually draws your attention to the white apple blossoms in the foreground.
I've also used another technique in this photo and framed the main subject in the lower right hand corner. Our eyes are trained to scan a photo from left to right, just as when reading. Therefore, the eye will be naturally drawn to the lower right corner of your photos.