We got an elf but I have no idea what the rules are, it's not the traditional one it's a cute cartoon character one, I just thought it would be a bit of fun, and what's nice is DH has got into it, he doesn't usually get all that excited about Christmas but this is something he's got into which is nice to see! We don't do anything elaborate, on Sunday he brought the Christmas tree out from under the stairs, yesterday he brought the advent calendars out and today he had packed DS's nursery bag, we don't tell him he's being watched and he doesn't do naughty stuff. But tbh DS doesn't even seem to be acknowledging it and isn't fussed, so I'm not sure if it's something we will keep up because if he's not buying into it then I do worry that like some others have said it might make Santa a little less believable. But we'll see how we go, I think we're being too boring with it which is why DS isn't noticing