The annual holiday bash isn't an invitation to go wild (unless you want office gossip to feed on your Dancing with the Stars moment). Therefore...
Stay in character. Pump up your usual style rather than making a radical switch. Sometimes it's enough to change shoes and add dressy accessories.
Think subtle. This is a chance to show co-workers your more glamorous side—discreetly. Forget anything overtly sexy.
Make an effort. Buttoned-up, business-as-usual suits or Casual Friday khakis suggest that you're clueless or lazy. Not a good message.
Avoid extremes. Your boss won't be impressed by the fabulousness of those crazy-high stiletto platforms; she'll merely think you're walking funny.
Keep it natural. Fragrance should be low-key and makeup only slightly heightened.