Rule reminder
In formal Italian, use 'Lei' (formal you) instead of 'tu'. Greetings change: 'ciao' is informal; 'buongiorno', 'buonasera', and 'salve' are formal. The formal imperative is 'si accomodi' (please sit down), not 'siediti'.
A client arrives at your office. How do you formally invite them to sit?