I don't know much about catnip, but the general thing about seeds is never let them dry out, but don't let them be wet either, just damp. Water from the bottom. Once sprouted, give them lots
of light. And for catnip, keep the cats away!
I did plant catnip, well grown plants, in my garden one time. The outdoor cats rolled it to death. Didn't eat it, just kept rolling on it. For awhile it would pop back up, but eventually it gave up.