My kitty is a nipaholic - he's ready for it anytime! If I get the plastic tub out of the cabinet, he starts "chirping" (making little short purr/meows in rapid succession), and as soon as I sprinkle some on the floor, he starts rolling in it and trying to grind it into his fur, especially on his head. If I give him the fresh leaves in the summer, I pinch them first to let the smell out, and he will bat at the leaf and chirp until I give it to him. The fresh leaves, he just gobbles up.

One time I made the mistake of giving him some nip, and then forgetting the tub on the table with the lid not tight - the next morning, of course, tipped over tub and catnip all over the kitchen! Good thing he didn't OD!