Ancona, Bologna, Catania
Mention the phonetic alphabet to a native-English speaker, and the first phrase that comes to mind is: "Alpha Bravo Charlie." It stands for ABC, and is used in the military to avoid miscommunication. It's also frequently used by anyone speaking on the phone (to a customer service represenative, for instance) to spell out words (or portions of those words) to confirm the correct spelling.
If it's necessary to sound out the spelling of a word in Italian, by convention the following cities (or alternate terms) are most commonly used to refer to each letter of the alphabet. The list of cities is not fixed. Therefore instead of "Catania," one could also use "Como," "Capri" or any other well known location. The only rule is to avoid a letter/town combination that could be mistaken for a different pair.
Italian Phonetic Alphabet
A come Ancona
B come Bologna
C come Catania (o Como)
D come Domodossola
E come Empoli (o Enna)
F come Firenze
G come Genova
H come Hotel (acca)
I come Imola
J come jolly (the joker in Italian card games)
K come Kursaal (kappa)
L come Livorno
M come Milano
N come Napoli
O come Otranto
P come Padova (Palermo or Pisa)
Q come Quadro
R come Roma
S come Savona (Sassari or Siena)
T come Torino
U come Udine
V come Verona (Venezia)
W come Washington (Wagner)
X come ics/xeres (xilofono)
Y come ipsilon (York or yacht)
Z come Zara (Zurigo or zeta)

