I Stole This from Esquire:
How to Attend a Party for the Shortest Possible Time

I figured with the holidays coming up some of you might find this useful. I promise to not bust you, if you don't bust me.

• Leave nothing at the coat check.
• The hosts deserve your respect and gratitude and are the only people who need to know you came. Immediately say hello and thank them for the invitation.
• Move around a lot so you get noticed. In the vital 15 minutes before you leave, slowly pull yourself away from the proceedings by talking to people who are closer to the door.
• Carrying drinks you're "supposed to deliver" is a great way to shorten a conversation. Keep your back to the door at all times, even when leaving.
• Enjoy yourself.
• Never explain why you're leaving unless pressed, in which case "the kids" is a universal, catchall exuse.
• Don't say goodbye. Send a thank-you note.

Couples probably need a little more extensive plan.

• Best to not seperate.
• Whoever is more directly connect to party should initiate steps towards leaving.
• Have signals worked out, so you don't bring up need to leave.
  
• Don't be caught checking watch. Try putting a vibrating alarm on your phone. Also looks like you just recieved a call. Incase "the kids" excuse doesn't apply.

I stole the first half of bullet points from Esquire. If you are interested in other similar articles- The Rules of Lateness, The Invitation Translator, How to Order Sea Bass in 7 Languages, and many more- then I suggest you pick up Esquire, The Big Black Book: The Style Manual For Successful Men.