You all know the rule of thirds. Yes?

Instead of putting your subject dead in the middle (Uncle Fred does this), you put it a third of the way from the right, the left, the top of the bottom. Or where those lines intersect. Like this:

Rule of Thirds, model Lindsay Biernat by Michael Willems

Uncle Fred would have put the model in the centre, but we find images more pleasing when we use off-centre composition like this.