Don't:

Bring an Uninvited Guest: Smaller parties may mean that spouses and partners   are not included in the festivities, even if they have been in years past. If   you're not sure if you can bring a guest, you should definitely ask. If it's   not indicated that a guest is invited, be polite and honor that request.

  Overindulge: It's still an extension of the office, so you should act in a professional   manner. You don't want to be the topic of conversation at the water cooler on   Monday morning. Also, do not to put anyone on the spot by asking why another   guest is abstaining from alcohol. We live in a health-conscious society. It's   a personal choice.

  Talk Shop: Keep business discussions very brief. If you've got spouses and partners   in the conversation, they often won't have any idea what you're going on about,   so you're just being a bore. Remember, too, that this is downtime. Don't burden   a coworker with your problems. Leave the office at the office.

  Gossip or Tell Off-Color Jokes: People tend to be a little more relaxed at office   parties, and if they have a few drinks, they may say things they normally would   not. Be mindful of what you say -- the jokes, the comments. We're human. We   want to have fun, but be mindful that it's a company event. There's still a   level of professionalism you must maintain.

Do:

Bring a Guest If You Can: It gives people a better idea of who you are as a   person. Your colleagues get to see another side of your life -- and you theirs.

  Get to Know Your Boss and Your Boss's Boss: Use the office party as an opportunity   to rub elbows with executives at your company with whom you don't usually interact.   You can't always get close to senior executives or partners at the office because   they're so busy, but in a social environment, they're more open to small talk.   Introduce yourself on a personal level and asking about hobbies or interests.   This is a key opportunity. Take advantage of it.

  Dress Professionally: This is an extension of the office. It's not the time   to wear the dress with the slit up to your hip. Wear something a bit more festive   than you might wear to work, but more conservative than what you would wear   to a nightclub. Keep an air of professionalism in mind when you choose your   attire.

  Keep Things Light and Fun: There's a lot of gloom and doom in the news -- and   perhaps at your company as well. Try to banish the dark clouds for the duration   of the party with a sunny attitude. It's tough for people to stay away from   these topics because that's all we hear all day long. But it can bring everybody's   mood down. Focus on positive events and the spirit of the season to avoid ruining   the party for your colleagues.