personally, i try to leave them as flat as possible and get my "kit" sound from the kick + OHs. The close-mic'd drums are brought up afterwards to add punch & power.

When i DO eq the OHs, it's generally using a HP filter to get rid of some of the mud in the low-end and occasionally, to notch out an annoying freq. (Ride-bell anybody? ugh!) that just won't sit in the mix. More often than not, a gentle compression on the OHs will smooth out the 'harshness' of bad cymbals

i don't highpass oh's

but sometimes i take out some "boxyness" in the snare to let the close mic have the punch... and sometimes some of the nasty frequencies in the cymbals.... and a gentle comp to smooth things out...

but some times i put in some 2.5k to add grunge.... combined with a comp set to do some hard pumping.....

it depends

No rules apply to OHs,

Although depending on what you want to achieve you could us EQ to add 'air' on the cymbal with a Hi shelf at 16K I find that works really well with a spaced pair confiq on jazz or ballad stuff.

But sure bad cymbals can be a real problem thats why your better off making sure that your kit sounds good before you even begin wondering how your going to get it to tape.