Formal:
* Tot ziens: This is the most common and formal way to say goodbye, similar to "goodbye" in English.
* Tot later: This means "see you later".
* Tot gauw: This means "see you soon".
* Dag: This is a less formal way to say goodbye, similar to "day" or "good day" in English.
Informal:
* Doei: This is a very casual and informal way to say goodbye.
* Dagje: This is another informal way to say goodbye, similar to "bye".
* Ciao: This is borrowed from Italian and is also very casual.
* Later: This is borrowed from English and is also very casual.
You can also use phrases like "tot morgen" (see you tomorrow) or "tot vanavond" (see you this evening) depending on the situation.
It's important to choose the appropriate goodbye based on your relationship with the person you are speaking to. In general, it's best to err on the side of formality, especially when you are first meeting someone or are in a professional setting.