Here in Bahia Blanca, Argentina (south of Buenos Aires province) it's rare to speak formally to your parents, although I had some neighbourhood friends who would do that, and it was weird (this was 15 years ago, of course).
Men kissing each other is a Buenos Aires (the city) custom as far as I know, I'm somewhat used to it because I travel there often, but I had a friend who was the only one who didn't travel to Buenos Aires more or less regularly and was very macho, he would look at you as if deciding whether to kill you with a hatchet or a butcher's knife if you even hinted at kissing him. We shake hands, except if there's a girl then we kiss. I don't kiss or shake hands with my immediate family and male friends, usually we just say hello or, in the case of a pre-breakfast-I-just-got-out-of-bed situation, a loud grunt
But then, I'm not a people person
Oh, and among young people it's common to use a different handshake, in which you grab the thumbs, sort of
It's informal and definitely not to be used with older people.
I agree with the don't-be-early rule, specially if picking up a date, you *never* show up early, since she probably won't be ready, and it'll be awkward, or she won't be able to open the door and you'll have to wait outside, or her parents will open the door and you'll have to spend 10 minutes talking with them (most guys don't like that heh).
*Never* take off your shoes, it's rude. We have welcome mats, use them if your shoes are dirty, although it's not required otherwise.
For the most part, if you visit someone expect to be fed until you are about to explode, and then more, the older the host, the more likely he is to do this... Refusing to eat is ok, though. I'ts also ok (and welcome) to bring food when visiting (in that case, the food is 'facturas', I'm not sure how to translate that type of food... it includes croissants). This applies to family as well, once when I was young I was visiting my grandparents and I didn't want to shower (their bathroom was cold and scary
) so I ate toast with honey for a couple of hours, my grandmother was so happy
My parents were a bit pissed when they arrived and saw I wasn't ready, though.
In Argentina there are a lot of different behaviours because it depends on the immigrants that arrived to the area, the particular immigrant family of the host (specially in this area, everybody is descended from an immigrant, Italian and Spanish mainly).
In Buenos Aires and here (we're very similar), lunch is between 12 and 14 (it doesn't take 2 hours, it's just that whatever lunch time you have, is inside that range), and dinner is between 20-22:30, unless it's a special occasion, then it might be much later. Usually between 16 and 18 there is a small meal (excellent time for facturas and mate). The no-call time is from 12 to 16 (lunch-siesta), although it's becoming less and less so. 15 years ago the city seemed to be a ghost town during those hours (it was great fun, actually).
Usually if in doubt, speak formally, or ask "lo puedo tutear?" (which is funny, since we don't use 'tu'!), two people under 30 will pretty much always use the informal, in mixed situations it's hard to say.
Don't be freaked out if someone apparently goes ballistic and starts insulting someone or something, it's quite normal, and after they finish the string of insults they'll frown and go on doing what they were doing (this is quite common in relation to traffic). Oh, drivers are insane, I think it's required by law, my motto while driving is "go kill yourself", it's what I say to all the nutty drivers when they do some dangerous maneuver (I let them go and hope they kill themselves and don't hurt me
), bus drivers in particular think they have a license to kill, bikers think they drive buses and pedestrians think they can fly (which is only true if hit by a bus). Expect to break the law, recently I was at an intersection and I waited for four full cycles of the traffic lights with no one letting me through, I had to go through a red light as it changed (so that all other cars were still), cars ignore pedestrians, so if they want to turn a corner, they will, and you better get out of the way.
Dressing lightly is quite ok, but no topless or nudity (except in certain spots), in beach towns it's not unusual for some people to go to the cinema barefoot (I'd recommend sandals, though).