Well, let's start in chronological order:
Geometric Period, 900 - 700 BCE
Very simple to remember, actually. This time period uses simple geometric shapes to create their figures. Nothing as complex as the later periods to be found here.
Archaic Period, 600 - 450 BCE
The time of the Archaic Smiles. All the figures created are smiling - even if they're on the brink of death. During this period we see a very subtle change in the way sculptures carry themselves: their waists are slightly moved forward, suggesting forward movement and better balance. The Archaic works also start to show more muscle detail in their figures.
Early Classical Period, 480 - 450 BCE
Here, we see the use of contrapposto - the whole human figure is no longer stiff. The shoulders and hips are usually angled towards each other to show natural balance. The head might be tilted for dynamic visual interest. The Greeks used a Canon of Proportions for the figures to appear more life-like and idealistic.
High Classical Period, 450 - 400 BCE
During this time, Athens was in power. Displays of power were shown through body movements instead of facial expressions. Also, the figures in a sculpture usually interacted with each other, though they could stand as an artwork just by themselves. The Greeks used a new extreme of realism and became more dramatic. They often used gods in their artworks.
Late Classical Period, 400 - 323 BCE
The Late Classical showed interest in people rather than gods. We start to see more relaxed figures with introspective feels to them, and we also see figures of women depicted nude appear. Sculptures start to occupy the viewers' space as well as their own. Often, they reach out towards the viewer.
Hellenistic Period, 323 - 31 BCE
Hellenistic sculptures wanted to evoke an emotional response from the viewer. Art became even more realistic and showed both Greek and other ethnic body types. We see the art become more melodramatic and start to depict everyday scenes from the lives of normal people.
