Party manners

I was raised with fairly strict rules with regard to to partying and other similar social interaction. I don't mean the kinds of rules that parents set for children while they are children, but the kind that are taught to children for later use in the adult world. You were supposed to assume that you are to come alone, unless told otherwise, and were not supposed to even ask; if the invitation was "avec", you were still supposed to ask about any specific companion you wanted to bring; there were no "open house" parties, etc.

When I grew up I figured out that first, these rules are not optimal for me, and second, the vast majority of the people I know follow a much looser set of rules. I have developed some new rules (or rather new ways) for myself, but I still wish for some explicit party etiquette rules, not necessarily because I want to adjust my own to them but because I would be nice to know what is considered normal, what is considered ok, what is definitely abnormal. Basically, etiquette is a matter on consensus and it's hard to have a consensus without a conversation, so I'd like some input on the following:

1. When there is a small group of people (2-3) who have decided to spend an evening together, as far as I am concerned it's a closed group and extra people can be brought in only after asking everyone's permission, and being the host of the party gives one no special privileges in this respect. No, this is not the moment to feel guilty for having brought some extra person to my place sometime. :) I am aware that not everybody follows the same rule, and rarely resent it, but I would feel quite uncomfortable asking a third person to join us without discussing it with the second person first. I am wondering how common is my way of doing this.

2. When there is somebody's party, and then some of the people, including the organizer of the party, move on to "jatkot" to somebody else's house, what are the rights and responsibilites of the original host vs. the new host? Or is this completely the new host's party at that point?

3. When somebody brings an extremely unacceptable person with them, what is the proper procedure for removing such person in general? How are the responsibilities of the host and the guest who brought the unappropriate person divided in the following cases: (a) if the guest knew that the person is unwelcome by host, (b) if the guest did not know that the person was unwelcome, (c) if the person was not unwelcome to begin with, but started behaving very badly during the party?

4. What is the proper procedure for letting people know who is unwelcome, especially in a context of a medium-to-large fairly open party? I remember once sending out an email that said "if I have forgotten somebody from this list by accident please bring them with you; X. was forgotten on purpose; anyone else can be assumed to have been forgotten by accident", but I don't think it was a correct thing to do. How do you let people know that a certain person is unwelcome?

(For all my curious friends here: if you don't know who is the one person who is very unwelcome to any of my parties it means that I believe that you are extremely unlikely to bring him there; if you are somebody who knows me through roleplaying or programming circles it's unlikely that you even know the obnoxious asshole.)

5. What is a proper procedure for letting people know that they should not bring anyone with them without clearing it with me first? I mean the situation when the party is generally avec but that particular person has previously exercised such a severe lack of judgement in choosing their avecs that I want them to pre-approve it with me.

(For all the paranoid friends here: there is one person like that and she knows who she is, so if you need to ask, then no, it's not you. Those of you who have been to the party in question: thanks for helping me to remove her avecs from my place.)

6. How do you let people know politely that they should not be sleeping over? This is quite relevant to me, especially during large and long parties - I need to communicate to people that they are welcome to party till the morning but I'd like them to go home afterwards as opposed to passing out in my bed and in random corners.