The bill, please.
CON-to — two syllables, stress on the first. Do not say 'check' — that is American English.
Said at the end of the meal when you are ready to pay. You must always ask — waiters will never bring the bill unsolicited.
'Conto' is the Italian word for 'bill' or 'account'. You can also wave your hand subtly and say just 'Il conto' without 'per favore', but adding it is always more courteous. In Italy, the waiter will never rush you with the bill.
Possiamo avere il conto?
Can we have the bill?
Slightly softer — 'possiamo' (can we) adds politeness
Ci porta il conto quando può?
Could you bring us the bill when you get a chance?
Very polite — ideal when the waiter is clearly busy
Vorremmo pagare.
We would like to pay.
Alternative that skips the word 'conto' altogether — equally understood
In Italy it is considered rude to split the bill in complicated ways. Common practice among friends is 'facciamo alla romana' (we go Dutch) — everyone pays an equal share, not what they individually ordered.