Blow your guests away by making potatoes the way fancy French chefs do — pommes a la Robuchon (as in Joel Robuchon).
Mashed potatoes should be equal parts potato and butter. Keep stirring cubes of cold butter into your hot mashed potatoes over low heat, and if the mixture gets shiny or breaks just add a splash of milk to bring it back together. As an old mentor of mine once explained, the goal is "potato-flavored butter."
Bonus tip: Save the wrappers from the butter sticks to place on top of your potatoes — they work even better than plastic wrap.