You should not sit at the first free table you see in a restaurant as it can be already booked. A waiter indicates free sets to guests.
Make sure you watch your belongings carefully in the crowded places. Despite the fact that the crime level in Nice is one of the lowest in the country, many citizens and guests of the city cannot protect themselves from dexterous pickpockets.
Locals really appreciate all attempts of visitors to speak their native language. Make sure you learn several phrases in French. This will not only easier the communication with citizens, but also will help to gain respect of hotels’ employees.
Street markets open very early. Many traders start closing their outlets already at the noon, so it's recommended to go shopping early.
If your French friends invite you to visit their home, you should not refuse in any case as it can hurt hospitable people. Friends should definitely present modest gifts. A bouquet of flowers and good wine will be enough.