Get input. Ask everyone what they liked and disliked from previous office Christmas parties. Have people select their three favorites to include in this year's party. Eliminate things that most people did not enjoy, especially if they were costly.
Make a list of possible venues, and designate someone to gather details on costs, availability, and amenities. Check sites in person to be sure your party will be accommodated according to your needs. You don't want to discover in mid party that bathrooms are not functional and accessible to all, or that the room is not large enough for your group, too little parking is available, or that too many other groups will be sharing the same space that night, leaving too little turn over time for setup and cleanup. Make reservations at least two months in advance to secure your desired venue.
Decide on a budget ceiling amount, then do your best to stay below it. Setting the budget in advance can help prevent costs from going out of control. Be realistic, though. Costs are very fluid from year to year. Take advantage of group discounts, sales and special offers.
Enlist everyone to help with decorating, choosing entertainment, and any other tasks, especially if you decide on a more casual gathering rather than a catered dinner. Place a sign up sheet in a prominent position, so that everyone has the opportunity to contribute to the fun.
Have a plan for the evening. Nominate an emcee. If you have a DJ dance, this task will usually fall to the DJ. Be sure to have ice breaker activities as well as entertainment. Office Christmas parties are a great opportunity for team building. Be sure to play a variety of music genres, and make learning a few party dances one of the evening's activities. Give prizes for the best effort, and any other categories you choose. Be sure to include places for quiet conversation as well as room enough for people to let down their hair and kick up their heels.
Be aware of any dietary needs when planning food and beverages. Have a variety of hot and cold appetizers available, and be sure to have salt free, fat free, sugar free and vegetarian alternatives as much as your budget will allow. Avoid or limit the number of salty snack foods served if you are going to serve alcohol, as salty foods encourage thirst and can lead to overindulgence in alcohol.
Have transportation available for anyone who overindulges in alcohol, or make arrangements for employees to stay in nearby hotels until the next morning. Employers can be held liable if they serve alcohol, someone leaves the party, and has an accident trying to get home.
Have a bartender, particularly if you are going to have an open bar. The bartender needs to have service training to know not to serve minors and to control the amount of alcohol per drink as well as to know when to cut anyone off.
Be sure to have security after the party to ensure that everyone gets safely to their cars and home.