These two photos are very similar, yet by moving the subject slightly left you get two different compositions. I did these to illustrate a point with my daughter about composition and subject placement. Either photo could work but the second one defines the face better... which might be important if you need to define the face better. The treatment of the face in the first one is easier to look at.
Then she tried it and came up with this shot.
Composition is a hard thing to teach, and I'm not a big fan of the rules of composition.
I speak at a lot of college classes and camera clubs. At these meetings people are always showing photographs that follow the rules of composition.
I think people like to follow the rules because it makes the work easy to defend or critique during discussions. I've heard all the rules, I've heard people explain that a photo works because of the triangular shape of the subject, or the inverted triangle of the subject, or the complementary colours working together, and lets not forget the rule of thirds.
Actually maybe we should.
I say forget all the rules, and I don't mean that you should learn the rules so you know when to break them.... forget them all together.
When you look at a photo you only need one guideline.... does it have impact or not. If it doesn't have any impact at all, just throw it away.