The degree of formality varies from person to person and from language to language. It won't come as a surprise that in German there is a clear distinction between the formal and informal way of saying 'you.'
The German language even has verbs to describe whether you are being formal or informal with the person you’re talking to. Duzen means to address someone informally, like you would with children, friends and family. The pronoun needed here is "du".
"Könntest du mir kurz helfen, Cem?"
Siezen means to be formal and expresses politeness and respect. It is commonly used in the workplace, when dealing with the authorities, with the elderly or with strangers. If you are unsure how to address the person you are talking to, address them with Sie and use their surname if necessary.
"Frau Lehmann, könnten Sie mir kurz helfen?"
Getting From Sie to Du
How to end these strange Germanic formalities though?
Easy — by asking politely.
If there is a noticeable age gap, it's the older person that offers this change in addressing one another. In the workplace it's the person who is superior in rank. In all other situations just take heart and go for it. This is what you could say:
"Ist es okay, wenn ich du sage?"
“Wollen wir uns duzen?”
"Wir können uns gern duzen, wenn du möchtest?"
Du Is Forever
Once you offer the "du" to someone, you cannot go back to Sie unless you really want to break things off with the other person. This would be considered a major affront – in a fifties kind of way. If the "du" came about at a boozy team event though, you might want to check if your boss remembers it too the next day at work.
The Berlin Way
In the German capital things are usually handled a little differently and it's fine to use "du" with almost everyone. Some might even be affronted to get a "Sie", wondering how much they must have aged recently to deserve this treatment. Don't forget though: doctors, university professors as well as police officers and any other state authorities are still off-limits.
There are two somewhat quirkier forms that follow a mix and match principle. The first one is the Hamburger Sie, where you are on a first-name basis but still use Sie. It's a smart way of being friendly in a formal setting, often used by the person superior in rank.
"Karolina, haben Sie schon den neuen Kollegen kennengelernt?" "Karolina, have you already met the new colleague?"
The Münchner Du is basically the opposite of the Hamburger Sie. You use "du" while addressing people with their surname. Apparently this is also popular with people working at the checkouts in a supermarket. So listen closely next time you are getting groceries.
"Herr Petersen, könntest du bitte mal das Fenster aufmachen?" "Mr. Petersen, could you please open the window?"