Watching the movie "The Puffy Chair" got me thinking about basic etiquette--lessons that should be obvious to everyone but clearly aren't.
1) Don't take phone calls when at dinner with someone. Like all rules there are exceptions--you have a preggers wife, for instance, and are waiting to hear how it went (though you probably should be at the hospital and not out at dinner with me). Taking a call during dinner is a way of saying "you're unimportant, and I am a slave to this ringing device". Better to turn the thing off, knowing that we survived a long time without cell phones and can just as easily return the call afterward.
2) Be on time. There's a reason we have a concept such as time. It's so that people can arrange things so that when one says "let's meet at five" the other can say "okay, since we both know what five o'clock means, that'll work". But hey, lo and behond one person shows up much later, which is a way of saying to the first party "time means little to a free spirit like me, and I don't mind you having to sit and wait for me". Here's a tip--if you don't think you can realistically make a pre-arranged time, let the other person know so they can expect you later. A simple concept that is lost on many.
3) When invited to a party, bring something. When hosting, don't actually ask guests to bring something. This one is trickier--it's expected that a guest not show up empty handed if possible, unless the host specifically says "just bring yourself" or if there's some other situation in which you can't pick something up on your way. Normally, you ask "is there anything I can bring" so all guests don't show up with the same bundt cake. As for the host, the only time the host should suggest a guest bring something is if it's called for due to the event--a pot luck dinner party, for example, since it's key to have a variety of dishes and to know what everyone's bringing. But BYOB shouldn't show up on an invitation any time after you're all out of high school, and guests shouldn't plan to just show up and mooch either.
4) Group dinners out and the cheque. This is often a clusterfuck. Ten people out, having a big dinner, then the check comes and it turns into the Geneva Conference. Sally had wine, and Bob only had a salad? How do we split that? Is it fair to split evenly if everyone had something different? This is one reason I prefer to do smaller groups, or pick places with a set price for everyone so there's no such haggling--it takes any dignity out of eating out. But when in this situation where one person ate surf and turf and Scotch and wants to split the bill evenly, and another person is acting the accountant, there should be some common rule--if the difference in the highest and lowest cost patron's meal is greater than say 10%, have the high cost patron toss in some extra cash. Otherwise, split it evenly--it's one of the costs of eating out in a group and if a few dollars of subsidizing someone else's meal is bothering you too much then don't eat out with that group again.