Typically, you will be introduced in a way that tells you how to address people. Someone might walk you around the office saying things like
This is Alex, who looks after all the database work
This is Ms Smith, the head of the department
And so on. Or people may introduce themselves to you
Hello, I'm Chris
Following a formal introduction, Ms Smith might respond
Please, call me Judy
If you don't get any cues like this then you won't know anyone's names anyway, so settle for "hello", "excuse me", and "good morning" and watch what they call each other. You'll figure it out pretty quickly.