it's all explained in this link:
http://www.martyfireball.f2s.com/DOD/getrecording.htm#recordingtipsfromthetop
"OH's are so difficult to get right, as you want to hear the cymbals but the Hi Hats will kill you if your not careful. I always try and mic cymbals in pairs, pretty close, towards the edge of the cymbal, away from the kit and hat.
With your o/h try filtering out from 500/ 600 hz down
Overheads are one of the hardest things to get right. Too much cymbals and hat and it will kill your mix, too little and you have no dynamics. I still struggle with OH's, it's down to the drummers style also. I usually go with 1 mic per 2 cymbals and try and keep the hi hat out of the oh's by obscuring the direct line of them with a cymbal. I always aim for the edge of the cymbals, about 1.5/ 2 foot above. I also get pretty heavy with the filtering and roll everything below 600 out. I dont tend to compress much as this just brings the hi hat out more, but if I'm mixing something with a lot of kit in the oh's, I'll limit them, maybe even send the snare to the limiter in the side chain. This can help the phasing of the snare also. Micing the ride from the underneath, near the bell, gives you good separation also.
I think cymbals are the hardest thing to get right. They can be an absolute nightmare. I try and get as much separation as possible, micing 2 cymbals per mic, if there's alot. Aiming for the edge and rolling everything out from at least 600 down. I'll sometimes compress the mids with a bandwith comp (c1) and try and get rid of more snare. Watch out for the hi hat also."