The concept of taking a photo where you "fill the frame" is not quite as simple as it may sound.  Yes, you want to fill your frame with your subject, but you also want to leave room in the frame for the subject to "move."

Let's take an honest look at this photo.  Pumpkins are the subject.  Perhaps more importantly, though, the subject is the variety of colors and textures of the pumpkins.  Depth of field is used to make it feel like they are "rolling" through the frame.

Fill your frame today.  Then take an honest look at your image and ask yourself if you have made your intended subject and, more importantly, the significant attributes of your subject absolutely clear to the viewer.

You'll have all week to practice this idea of filling the frame.  Have fun!