BLUSH SHOULDN'T LOOK TOO BRIGHT OR TOO OBVIOUS...
and you should apply just enough to help your own 'glow' shine through.
Here's how to do just that...
* Blush should be well-blended around the edges so you don't see circles or stripes. To do this, use a big dome-shaped brush to spread colour sheerly so you can gradually build intensity, as opposed to going full-on bright circles at once.
* When you're done brushing on your blush, blend around the edges with a sponge or puff: Blending it down makes the colour even sheerer and more believable looking. You can use just a regular wedge-shaped foundation sponge to do this.
* Pick colours that mimic the actual flush your cheeks get. And the darker your skin, the deeper the shade, that way it'll show up. Darker skin with blush that's too light will make you look sallow.
* Save shimmer-flecked powder blush for evening. In daylight it'll look fake and the shimmer will make your skin look more dry and bumpy. Instead, opt for really fine silky formulas.