I know there are many different Icelandic greetings (Halló, Hæ, Sæl, Góðdan daginn, Hvernig hefur þú það?, etc.), but I am not really sure which one of these is best to use in a given situation. For example, here are some specific situations: I run into a friend/acquaintance (e.g. in the hallway at school) and I want to say something quick and informal (something like "Hey, what's up?" or "Hey, how's it going?" in American English). One of my friends introduces me to one of his friends and I say hi to this person for the first time ("Hi, nice to meet you."). I walk into a shop and say hi to the shopkeeper whom I don't know (just to be polite). I meet an old friend whom I haven't seen in a long time. I know that things have been rough for him lately and I want to ask sincerely something sincere like: "Hi John, how are you doing? How is everything? How are things going for you these days?" Finally, I am wondering if there are more informal greetings used in Icelandic that wouldn't appear in a textbook? If I think of English, for example, I know that in real life we often use greetings that wouldn't be mentioned in a beginner's textbook (and the greetings students do learn are often too formal or "stiff").