Company parties tend to be rote so therein lies a fine opportunity to bust out of the office box and make a party that is particularly fantastic. Take care to add elements of surprise and delight.
For formal/large parties, keep attention to the feel of the broader space, it ought to convey respect and coziness. Be sure to see to the finer details like table arrangements. Seating assignments are everything. Draft a chart and then ask two people what they think of it. Do not ask questions at this stage, just employ their recommendations. Listen to all the stories, repeat nothing and people will continue to tell you what they think of your seating arrangements unabashedly for all of your party planning years to come.
Keep hold of the objective of the party, the essence, which is the kind of gift you want to give and check-in to see how the party is shaping-up to it. Make adjustments on the fly if you can carry them out covertly and without hurting anyone. Otherwise let it go.
A party is a gift to many in one shot, and your job as the party maven is to be sure the gift is delivered.
What has made all the difference in your company parties?