Partier, Know Thyself
The #1 thing you need to know going into a kinky party is yourself. What are you hoping to get out of the experience? Get as specific as you can. Do you want to get laid? Are you hoping to find someone who can give you a taste of pain? Do you want to look and not touch while meeting people?
It's common, as a newbie, to say to yourself (and others), "Oh, I'm not here for anything specific; I just want to see what's there." While the open-mindedness is great, the lack of specificity spooks old hands off and makes it less likely that you'll get what you're, after your first time. You don't have to lock yourself into something obsessively specific, but you need a place to start.
Filling out one of the many online BDSM checklists is a great way to learn more about your interests. Most of them differentiate between things you'd like to try and things you would try but aren't necessarily drawn to, which is a nice way of getting a bead on your current interests and the breadth of what you might end up exploring.
Know Your Party, Too
Every kinky party is different. Believe it or not, there are even very strong regional differences, so reading generic guidelines will only get you so far. If the organization throwing the party has a mailing list, get on it. If they have a website with a contact email, drop them a line! Be honest: It's your first party, and you'd like to know if they have any advice for first-timers.
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Many people avoid doing this because they think displaying their newness is a sign of weakness. However, being forward and proactive about gathering necessary information to behave appropriately and safely suggests that you're responsible — which is a big deal in this community. And, frankly, "fresh meat" is deeply exciting to most local scenes as well, so trust me: you won't end up with people running away from you because you're new. Just the opposite!
The response you receive from an organizational contact will be specific to their locale and this group, which is priceless. For example, one of my locals runs a wonderfully tight ship requiring attendance at an orientation meeting, and they are the only place I know that has a rule against walking across the dungeon; you must move around the edges of the room to avoid distracting players. If you only knew the rules for one of my other locals, which is run in a much looser, casual style, you'd be in for a pretty difficult night.
Know The Commandments
While every party is different, some rules are pretty much universal, to the point that many "old hands" may forget to mention them. Here's your cheat sheet.
Do not touch. Consider this the primary rule. Do not touch any person, implement, luggage, or other personal effects unless and until you have been given an explicit invitation. There are many reasons for this, but at your first party, you only need to worry about keeping your hands to yourself.
Stand back. Whether people are having sex in front of you, flogging one another, executing needle scenes, or kneeling at one another's feet, keep your distance. If you look for it, most parties have some kind of indicator about where you should be: there may be a row of chairs, or an obvious "walkway" between stations. Watching from a discreet distance is almost always allowed and encouraged.
Be completely honest. This is not the time to puff up any kink experience you've had. If someone asks whether you've played with bondage before and you haven't, you'd best be answering "no" straight up. I know how hard this is from experience; when I was asked at my first play party about my experience, I had written kink fiction for years and had a huge library of kink nonfiction, so I knew all the technical stuff, but I had no hands-on experience. It was nerve-wracking, trying to explain that in a way that didn't make me sound like a creeper or a "fantasy" player and hoping it wouldn't scare off the old hand who'd shown some interest in me. It was the right thing to do, though: a scene gained by exaggerating experience cannot go well.
Know when to speak. Most parties will have at least one room set aside for socializing — usually the one where snacks are kept. If everyone seems to be chatting in a fairly typical party atmosphere, this is where you politely introduce yourself and ask questions. And do ask questions! This is how you get what you want: by talking about what brought you here. Surprising and almost magical connections can happen at this point if you're honest and open. (One caveat: Even in casual chatting rooms, if you ask a question of someone who does not respond, let it go. Some submissives and slaves are under orders not to speak to anyone but their partner. Initially, it's better to assume that's what's happening and walk away rather than try to figure out whether that's what's going on.)
Know when to zip it. Most parties will also have areas where actual play is occurring and the conversation is less, or confined to each scene in itself. This is the place to be quiet and watch. Every party has its own tolerance level for chatting inside play areas, but none will be upset with silence.
Go easy on the honorifics. She may look like a domme, but you need not call her "ma'am"; he may look like a sub, but you'd best not call him "boy." While every locale and club will have different preferences about this, no one will give a newbie too much of a hard time for not instantly knowing who to call what (and if they do, you know that's not a good place for newbies). However, making assumptions about roles can get you in a lot of trouble very quickly. For example, while my partner is good-natured about it, he's often been "mistaken" for a boy, due to his appearance when, in fact, he owns a slave. As for me, I'm a pangendered switch, so the odds of attaching the proper honorific to me by guessing is pretty much nil!
When The Party's Over
Your first kink party is a great opportunity, but it's only that: an opportunity. If it goes poorly, don't assume you're not cut out for the dungeon; it may just be that particular entrance that's not working for you. My first party was cool, but it wasn't the best or most comfortable one I've been to. Allow yourself the possibility of trying out others if the concept worked for you, but the night just didn't.