Receive a handful of treats from one of the Candy Buckets located in an inn.
For the "Tricks and Treats..." series of achievements, I recommend installing the add-on Candy Buckets (Hallow's End). It adds small candy bucket icons to your world map, and even knows and remembers buckets you've visited! It has TomTom (and TomTomLite for those users) integration, too. Spiffy!