‘ArrivederLa’ is a more formal way to say ‘arrivederci’. But isn’t ‘arrivederci’ already formal? It is definitely more formal than ‘ciao’ but there may be a situation where you need to increase the degree of formality even more, to demonstrate your respect and politeness.
You use ‘arrivederLa’ when you are speaking to one person, the ‘ci’ in ‘arrivederci’, is the plural version. If you speak to an elderly person, it’s a good idea to use ‘arrivederLa’ – it won’t sound pompous or pretentious, it will only highlight your respect.
Of course, situations may differ. You can be super-informal with your grandma or on friendly terms with all the big bosses at work. However, when dealing with a foreign culture, it is best to be a bit on the 
formal side at first before you get to know the people and the culture better.
10. How to say ‘See you later’ in Italian – A dopo
‘A dopo’ is an Italian equivalent of the English ‘see you later’ but is only used when you’re actually going to see the person again later that day.
Imagine seeing a foreign guest off at the airport and they say ‘see you soon’. It is not that big of a mistake, but it feels weird as you are unlikely to see them again soon or maybe at all.
11. How to say ‘See you soon’ in Italian – A presto
Italians take their goodbyes seriously. Or, to be more exact, literally. Similar to the previous example, do not say ‘a presto’ if you are not going to see the person soon.
If you are leaving work for the day and saying goodbye to your colleagues who you will see the next day – great. If you have been traveling in Italy and are leaving to go back to your home country – this is not the best choice. Instead, saying ‘arrivederci’ would be more appropriate.
12. How to say ‘See you tomorrow’ in Italian – A domani
Can you see the pattern yet? ‘A’ followed by a time frame will specify when you plan on seeing the person again – in this case ‘domani’ (tomorrow). It goes without saying that you would only say ‘a domani’ when you’re actually going to see the person the next day, like a friend, tour guide or to the barista at the cafe where you get your morning coffee.
13. How to say ‘See you in a bit’ in Italian – A tra poco / A fra poco
How to pronounce it: ah tra poh koh / ah fra poh-koh Meaning: See you in a bit (literally, until a little) Usage: Informal Italian greeting
‘A tra poco’ or ‘a fra poco’ can be used interchangeably with ‘a dopo’. Perhaps, you are running a little late for a meeting with a friend and you are calling to say that you’re almost there and will see them in a few minutes – you can finish your call with ‘a tra poco’.
14. How to say ‘See you’ in Italian – Ci vediamo
Just like ‘a presto’, ‘ci vediamo’ should be used when you are going to (or hoping to) see the person again soon. For example, if you’re having breakfast with a friend who you will see that evening at a party, you could say: Ci vediamo stasera, buona giornata! – I’ll see you tonight, have a good day!
15. How to say ‘Bye’ in informal Italian – Ti saluto! Vi saluto!
How to pronounce it: tee sah-loo-toh / vi sah-loo-toh Meaning: See you, bye (literally, I salute you) Usage: Informal Italian greeting