This is the most important formal greeting in German. You can use it throughout the day.
Depending on the time of day, you can also use:
Guten Morgen – until about 11 a.m.
Guten Abend – as of about 6 p.m.
When you greet another person, you offer your hand for a handshake and look them in the eye in a friendly way.
This is how you greet friends, acquaintances and young people. You can also just smile, offer a handshake, or nod to them.
Some people hug or give each other a kiss on the cheek.
There are lots of different options in everyday language.
You can say this to people you know well and see on a regular basis. It more or less means: "Hello, everything ok with you?" or "Hello, what's up?" The easiest way to respond is to ask the same question back: "Na?"
In some regions there are particular greetings, such as:
Servus! – especially in Bavaria and Austria, informal
Grüß Gott! – Southern Germany and Austria
Grüezi! – Switzerland
Moin! – Northern Germany