To determine your face shape go to this website.
( http://www.hairfinder.com/tips/faceshape.htm )
It is equally important to have a good Blush Brush and a blush color that matches your skin well. It is said that the color of your blush should be more or less the same as the color of your cheeks after you exercise. That's your natural color. Personally, I think you can experiment and try other colors just as long as you do not stray too far from your natural cheek color. I use Vanora from Ocean Mist Cosmetics and a medium pink blush.
Flawless Face Brush
Now that you know what your face shape is, you are ready to apply your blush. in this interactive webpage it will show you where to put your blush and highlighter.
Go tot his website
( http://www.laurenscarlet.tv/makeup/5-03_faceshape.html )
I hope this helps!