Look, you're about to go down a slippery slope here. Sure, there are probably one or two people in your office to whom you like to show your O face, but should you?
Hell yeah! Don't let your stupid conscience get in the way. It's the holidays! This is as good of time as any.
You've got plenty of time off from work, so if you're good at avoiding people for the few days you're in the office you can probably avoid the hell out of this person until after the first of the year. By then, it will probably be forgotten about.
And besides, it's the time of year for giving and plenty of people give it up in these situations each holiday season. You're not going to be the first or the last, but you need to follow some rules to make sure you do it right.
Booze is your friend.
Now don't use this as a license to get blotto and make a fool out of yourself. Then you'll really look like an idiot. No one likes the holiday party drunk; simply get slightly lubed up so your inhibitions – and perhaps your moral compass – go out the window. You don't need that fuckin' thing anyway.
More importantly, make sure to feed your intended target enough drinks to make sure they lose a few things out the window, too.
Blatantly hitting on someone or being on the prowl is as bad as being the holiday party drunk in most situations. Then people will forever remember you as “that guy” or “that slut.” Who the hell wants that? It's like having your license to bang people at the office revoked.
Flirt discreetly, don't make a scene – and if you can close the deal, leave separately. If you're the idiot who ends up making out with someone in the middle of the office party, you might want to think about calling in sick…forever.
Your best chances of getting laid at the office party is to not be at the office party. First, make sure that you've made your presence known to your superiors and colleagues. Then focus on the task at hand.
If things are going swimmingly with that certain someone, suggest going somewhere else for a drink. It's more intimate and conducive to sealing the deal. Plus, you're away from prying eyes.
Similarly, don't steal away to the copy room or the staff bathroom at the party to try to make it happen without exiting the premises. You'll always get caught and you don't want to be that fool.
Avoid people you work with directly.
It's much easier to work with someone you haven't slept with. You probably know that going into this, so imagine how hard it would be to work directly with someone every, single day after you boffed him or her at the holiday party while you were piss drunk.
Instead go for someone you see once in a while or – better yet – someone you never see at all. Always go up the company ladder, not down. And at the very least, go horizontally.
That way you'll better avoid hurt feelings, awkwardness, lack of professionalism, and sexual harassment lawsuits.
Act normal afterward.
You're probably going to wonder how to act when you see this person in the office. Just go about your day like usual, only a little nicer. Maybe even flirty… but not too flirty, unless you're planning a return engagement.
Whatever you do, don't be cold. Someone in your office did you a favor (or made as big of a mistake as you did) and they probably feel weird about it, too. But hat doesn't mean you need to act like a jerk; it will only make things worse.
If you need to discuss the incident, have a drink during happy hour to do it. So long as you've followed the rules above and haven't made an ass out of yourself in front of everyone, you'll be just fine.
Because in the end, we're all professionals here. Aren't we?