I am always ranting on here, it is so bad. Oh well! :) Here are some real-life pieces of etiquette that some might find handy:
1. If you want to see someone else, get in touch with that person. That's right, direct communication is the best thing.
2. If I say I am going to organize a party, don't take over planning the details, contacting people involved, or starting a guest list. Sorry, you're over-functioning.
3. Don't ask about a party before you've been invited. In other words, don't fish for invitations. Just chill...you'll be invited.
4. DO reply to communications (such as invitations, planning emails, etc) about parties in a timely manner, preferably within 24 hours.
5. Let your yes be yes and your no be no: inform the host as soon as possible whether or not you will be able to attend an event. A "maybe" does not suffice for a polite answer--respond affirmatively or negatively as soon as you know either way. (Exception: Facebook events are typically more informal and may not need a definite yes or no...but you should RSVP with a yes, no, or maybe nonetheless.)
6. In Church, when going up for the Communion, if several people are sharing a single kneeler, it is the job of the last person on that kneeler to raise it after its occupants go up for Communion; it is the responsibility of the first person back to lower it for the rest of its occupants. Following this simple rule makes it less confusing for everyone! (Exception: gentlemen have the prerogative both to raise and lower the pew for a lady/ladies.)
7. In an office environment, do not hover around others' desks. If you have something to communicate, knock on the door or lintel of the office before entering, or say, "Excuse me," and then begin your communication.
That's all for now, but I'm sure I will think of more!