Once the foot of the sock is about as long as your foot without your toes, it's time to do the toe shaping. This is usually accomplished by evenly decreasing along both sides of the foot to get a nice, rounded toe shape.
There are many different ways to form a toe that can be quite decorative. When the number of stitches has been decreased to about a quarter of what you started out with, the toe is commonly closed with a technique known as grafting or the Kitchener Stitch.
In the picture at right, the toe is the part knit in green.