I would recommend placing the cymbol mics at least 3 to 4 feet above the cymbols. This will help them to pick up less of the kit and let the sound from the cymbols develope more. I do, however, place a mic on the hats, just incase you need more of them in relation to the other cymbols. As for other mic placements, make sure the mics are close to the drum heads, and pointed in the right place. You mainly just have to really take time to adjust the mic placements to make sure you're getting the best sound and that rejection of the rest of the kit is reasonable.