Formal you
Lei
We've already seen that lei means she. But Lei is also used to be polite when talking to just one person.
In general, you'll use tu in friendly conversations or with children; use Lei in more formal situations or when talking to adults you don't know.
Lavoro per Lei.
I work for you.
Scusi, chi è Lei?
Excuse me, who are you?
Notice that the verb form for lei is the same whether you want to say you or she. Usually, though, Lei is spelled with a capital L when it means you.
Sì, lei è molto più alta di me.
Yes, she is much taller than me.
Sì, Lei è molto professionale.
Yes, you are very professional.
La prego di entrare
To ask for something very politely, you can use the expressions La prego di and La preghiamo di followed by an infinitive.
La prego di arrivare presto.
Please arrive early.
La preghiamo di venire con noi.
Please come with us.
These expressions are especially common in written Italian.