Even if your store provides them, do not include little cards that contain information about your registry. And don't add the registry information to your invitation itself in any other way. It's impolite for you to start the conversation about gifts. Even if some guests find it convenient, others will think it seems greedy. Ask family and friend to spread the news when people ask; you can also put this information one level down on a wedding website, and mention it to anyone who asks you directly.