Here is a quick guide to help you out with the use of a blush-
1) Clean your face properly. Know what color suits you the best. Both the color of your foundation and the blush should compliment your face, as well as each other.
2) Apply foundation first and complete your eye makeup before you go for the blush.
3) The blush should be the last or the second last coat of makeup that goes on your face.
4) Get hold of the perfect brush for applying your blush. Do not use the same brush which you use for your foundation.