Hint: Wisp's Lamp

On some nights after 8, you may run across Wisp. A voice will talk to you when you arrive -- he's always near water. Follow its directions until you find the source of the voice, which is a ghost named Wisp. He tells you that he lost his lamp and needs you to find it (for a pretty reward, of course!) You should then meet him in the attic of your house once the lamp is found. For doing this for him, he'll grant you one wish. You can ask him to clear your town of weeds, clear your town of cockroaches, or give you a randomized item.
You may find the lamp before Wisp appears as you go about your normal wheelings and dealings. If so, you'll know he'll appear somewhere that night to claim it.