One question that we need to get out of the way first is the problem of shame. Shame is a morning-after type thing, the knowledge of having done something dreadful coupled with an inability to remember what. During the course of the morning, memories of what you did will come back to you (of their own accord or via the telephone) and shame will give way to abject horror. 
It's important to make a distinction here between appalling behaviour and things you should not have done. Was it wise to take off your clothes and demonstrate the skills you picked up in a Vietnamese brothel? No, of course it wasn't. Is it the most embarrassing thing you ever did? Probably, yes. Should you have done it? Definitely. The rest of us loved it. Now we have something to talk about for the next few days - everything from your stretch marks to the trick with the ping-pong balls. As for looking people in the face again, phone everybody and insist they come out for drinks. The time to worry about your actions is before you behave badly. If you can't deal with shame, don't act like an arsehole.

Are there rules for this sort of thing?
There sure are. The broadest guideline is to ensure your behaviour is appropriate to the situation. At the beginning of the evening, it is appropriate to smile, chat and tell the hostess how lovely she looks - no matter that she's dressed like a rail crash in Munchkin land. With four bottles of wine and a half dozen vodka martinis inside you, it is appropriate to be screaming, "Hurt me, big boy, hurt me good", from the cupboard under the stairs.

What to put on the invitations?
This depends on what you think will happen. If you expect a small number of people who will make amusing conversation, call it a 'gathering'. There are people, though, who will mistake this for a coven meeting and you may end up with more than you bargained for. Particularly unbearable folk give 'soirees' or an 'at home with...', so there's a thought for you. If you have no idea how many people you invited but are reasonably confident of  the police arriving, go ahead and call it a party.

NB: A dinner party is not a party, it is a meal. Do not invite gay people in order to "provide a bit of colour". All this means is that you are showing off to your drab, hetty friends. Any half-way intelligent queen will drink all of your best whisky, give drugs to the best looking man in the room and then seduce him. If that's your husband, you've got no-one to blame but yourself.

How should I dress?
Again, the key word is 'appropriate'. If you are invited to a fancy dress party, dress in a comfy sweat shirt, old jeans and a ratty old pair of trainers. And stay home. No-one with the least talent or imagination needs to wear a costume to disgrace themselves. And we don't want to party with people who do. Let's all say it out loud: FANCY DRESS IS FOR LOSERS. There now, don't you feel better? Drag, on the other hand, is a different matter but only so long as it is worn by gay people and does not lead to the wearer miming to show tunes, claiming to be a cabaret act. Members of the clergy, of course, can wear whatever drag they want: it's a perk of the job. 
Generally, you should dress according to how you plan to behave. If you feel mysterious, wear something concealing, like a tea-chest. If you feel like being popular, wear something you can comfortably kneel in (come on, keep up). No matter how long you've been single, though, it is not correct form to wear a wedding dress - unless, of course, the party is for the wedding of someone you heartily dislike.

What should I do about supplies?
Buy in a little booze to get the evening started, ensure everyone brings plenty of their own and invite a well-stocked drug dealer. If you are going to someone else's party, bear in mind that booze always runs out: make sure you know all the good places to hide bottles. That way you can find some other cheap bastard's drink when you have finished all your own. Take with you whatever spirit makes you feel frisky but on no account should this be gin. There is nothing more tiresome than a gin-soaked queen crying her eyes out and demanding all the attention in the room. Ask anyone who's met Princess Margaret. 
Drug etiquette is de rigeur at parties. If you don't want to offer it to everybody, don't pull it out in a crowd (this goes for more than just drugs, actually). And make sure you're with someone who knows how to shut you up. If you're anything like me, you tend to stop talking some hours after you ran out of things to say.

Oh God! There's the food to do, as well.
There are two types of party food: traditional and responsible. Traditional party food is full of strong flavours, dripping in gooey sauces and served in bite-sized portions. This is to make it easier to vomit when you're drunk. Responsible food is stodgy: it is designed to soak up alcohol and prevent you from vomiting. This means that your hostess has just redecorated and doesn't want sick all up her walls. You should loudly admire her good taste. Naturally, if there's the correct amount of amphetamines going round, no-one will touch the food anyway. It will sit around, going greasy and cold until someone starts a food fight. Shame about the new wallpaper. And I did so like it.

What about sex?
We'll have to make it quick. I'm expecting guests. 
No, I mean what are the rules of sex at parties?
Oh, I see. Most people behave as though having bad sex with terrible people in stupid places is the whole point of parties. And it is. Nevertheless, there are certain rules that need to be kept in mind. Whilst the purpose of parties is undoubtedly sex, the purpose of sex is to create gossip. It follows that your performance should be judged so that people will talk about it for weeks to each other but still talk to you as well. 
Consider others when choosing a venue. Fucking someone up against the beer fridge means that nobody can get a drink until you're done (I've found). Many people consider it bad form to get laid in the bathroom, but I'm not so sure. It's often the only door with a lock and anyone waiting can always use the garden. A friend of mine makes a speciality of getting laid in the bathroom at parties. She can draw a cheering crowd by virtue of the fact that she has noisier climaxes than Wagner. If there is a spare bed, though, you should really use that. Convention dictates that body fluids can reasonably be left on bed linen, but not table linen. Also, don't leave compromising stains on the host's clothing. Particularly if it's still hanging in the wardrobe. 
If you are the host, there are specific rules about who you should fuck. Always fuck somebody of the opposite sex to your partner: it puts you in an automatic position of strength during the subsequent argument - "It's not as though it was another woman, darling. Besides, Kurt is a Romanian gymnast." If you plan things properly, you can make great strategic gains from drunken infidelity. Make sure that the person you screw is someone who everybody knows you can't stand. For one thing, the surprise value is that much greater and this translates into big gossip points. Also, your partner will make the amateur psychology link between strong professed dislike and hidden sexual attraction. In future, she will dump those of her friends you don't like instead of inviting them round the whole time and telling you to grow up.

Is that everything?
It's all I can think of for now. I expect I'll come up with something else in time and, when I do, I'll let you know. When you think about it, it isn't all that likely that you're going to remember all this stuff anyway, particularly when you're blind drunk with a couple of the other guests in your mouth. I sure as hell never do. But remember this; there are two sorts of party people. There are reptiles and pondlife. If you're still worried about being a reptile, ask yourself - which one eats which?