Witch hazel is a sure thing that will shrink pores. But don't use it straight out of the bottle because I can be really harsh. Dilute it with water until it doesn't to strong on your face.
I've used half of a lemon with honey on top and I rubbed it over the areas where I had black heads. Exfoliating with something that has a very fine, grainy texture can help clear all of the dirt out of your pores. Then steam your face to open up your pores and use your index fingers to squeeze the blackheads out. Also, make sure the products you use say non-comedogenic.
Unfortunately, you can't completely get rid of blackheads, especially not at once. Getting a facial every so often can help because an Aesthetician can better see all of blackheads you have through a magnifying lamp.
I hope this helped :-)