Buy a sharpie at your local drug store. I think it sould read do "not" use a water based marcker.
Write on the inside clear part of the CDR. Some people I know say that the ink can effect the dye on the other side when written on the panted side. I'm not sure of this, but it doesn't hurt and it is better to be safe than sorry.
Also, for information concerning CDR's check out this site.
www.cdrmediaworld.com "They have great information"