I love blusher, a tiny amount makes such a difference to how I look. I am no expert but here is what I (think I) know:
3 basic kinds: powder, cream and stain.
Cream is freshest looking. Powder is easiest to build up gradually. With either, start with a tiny amount, blend really really well, and add more as required. Always apply in natural light if you can - bright artificial light will wash out the colour so may lead to you overdoing it by mistake.
Stain is IMO only for the experienced - though Benefit's Benetint and Posietint are supposed to be reasonably easy to use.
It should go on the "apple" of your cheek - smile, and see where the cheek rounds, that is where you should put blusher (as that is where would naturally flush when you are hot/cold/flustered etc). But obviously need to blend well (as above) to avoid clown look.
If you wear foundation/BB cream/tinted moisturiser, apply blusher afterwards.
NARS are often recommended as having shades that suit everyone. I like Clinique, they don't do many shades but they are all pretty non scary. The bareMinerals ones and Boots Natural Collection ones are worth a look too I reckon.