I own some NOS shifters, Campy Athena 9 speed, from 1998 i guess. do you guys know if I can use it with any campagnolo front/rear derailleur? how do I know what is compatible?
This page is incredibly useful for figuring this stuff out. Campy shifters with just about any front derailleur should be fine since they have micro trim.
You will need a pre-2000 rear derailleur as the cable pull ratio was changed in MY2001 and the lever / rear derailleur movement artio, if you use a current 9/10s RD will not give you accurate indexing.
You can use and front derailleur from Campagnolo describing itself as "9/10s" compatible but you may find that you need to set it up with more care as the most recent 9/10s FDs have a different movement to cable recovery ratio, too - this is not such a big problem on the FD as it is on the rear, because you are not aiming for such exact index points but it can still be a consideration.
As the main Campagnolo factory-appointed Warranty and Service Centre for the UK, we can assure you that the above answer is correct.