Here are a few hints to turn the experience to your advantage and really stand out from the rest of the crowd.
Plan. Plan to attend and expect to enjoy yourself; and plan who you want to contact and what you want to accomplish at the party.
Check. Make sure you know where the party is located, what attire is appropriate, if spouses/guests are welcome, etc.
Arrive shortly after the event starts. Party goers (especially you) are still fresh and alert.
Seek out the hosts, thank them for the invitation - make a little small talk, then move on so others can do the same.
Mingle. Introduce yourself to someone you don't know. Tell your clients/coworkers how much you have enjoyed working with them and their support during the past year.
Sample a few items from the buffet. Be sure to select things you can eat neatly, with one hand, while standing up.
Moderate what you drink. Keep reminding yourself that this is a business event first and a party second. There is nothing wrong with partying "sans alcohol". No one else will know.
Seek out and speak to the people at the party who can influence your business/career. Talk to the client's employees you normally would not meet. Chat briefly with them about their interests or anything you have in common.
Keep your glass in your left hand so when you shake hands with someone, your hand isn't wet or cold.
As you leave, thank your hosts - if you know the people on the party committee, thank them too.
Followup. If you told someone you would deliver information to them etc. make sure you followup on the next business day and deliver on those promises.
Not the mingling type? Then find someone who looks as miserable as you feel and speak to them. You'll both enjoy the evening more.
Stay away from salty or greasy foods that make you want to drink more. Choose foods high in starch and protein that will help slow the absorption of alcohol.