A traditional wood-mounted rubber stamp should be cleaned after each stamping session - if using an all-purpose water-based ink, then usually you can just blot on a damp paper towel. If using permanent ink, thicker inks (like metallic or fabric inks), or if switching to a different ink color next time, then it can be cleaned with a rubber stamp cleaner (see cleaner instructions).
Even if using the plain water-based inkpad to stamp with, cleaning the stamp periodically with a rubber stamp cleaner will help to keep the rubber in good condition, and it may even help rejuvenate older stamps as well.
Make sure stamp is dry (air-dry) before storing. Keep stamps out of extreme temperatures, out of direct sunlight, and in a safe place.