Turkish has two forms of you – sen and siz (like the French tu and vous) – the first is singular/informal, and the second is plural/formal. Generally you should use the formal one, unless speaking to someone you know well.
In most situations greeting someone has several parts:
The first part – saying hello
Both parties say Merhaba Hello, or depending on time of day perhaps one of the following:
Günaydın Good morning
İyi günler Good day (may be used throughout the day)
İyi akşamlar Good evening
On meeting someone for the first time:
Memnun oldum Pleased to meet you.
The other person responds with:
Ben de memnun oldum. Pleased to meet you too.
The second part – asking about health
Nasılsınız? (singular/informal Nasılsın?) How are you?
The response is: İyiyim, teşekkür ederim/teşekkürler I am well, thank you/thanks
This is followed by asking the same question in return:
Siz nasılsınız? How are you? (or Sen nasılsın?)
The other person replies Ben de iyiyim, teşekkür ederim I am fine too.