You can contour your face by using a foundation a shade or two darker than your usual foundation to create "hollows". Where you put the contouring depends on the shape of your face to begin with. The most popular face shape is oval (most movie stars have oval faces, or look like they do).
You will apply contour to the hollows of the cheeks, the sides of the chin or the wide parts of the forehead to make them appear to recede slightly, giving an overall shape that's more oval than round or square.
As well as using makeup for contouring, you can create highlights by using shades lighter than your usual foundation color. A line of lighter foundation down the bridge of the nose can create the illusion of a straighter nose; a little dab on the apples of the cheeks appear to make them higher.
The most important thing about contouring is not to lose perspective. Make sure the light you're making up with is the same as the light you'll be seen in. Take a step back now and then to make sure you're not going overboard or creating a clowny or geisha face if you aren't going on the stage. And remember there is only so much makeup can do; life doesn't come with an airbrush, and the round face that you think is the bane of your existence may seem quite beautiful to someone else.
