Tipping at a Restaurant

You want to leave a tip and aren't sure about local customs.

You
Disculpe, ¿la propina está incluida en la cuenta?
dees-KOOL-peh, lah proh-PEE-nah ehs-TAH een-kloo-EE-dah ehn lah KWEHN-tah?
Excuse me, is the tip included in the check?
In some countries, a service charge ("servicio") is automatically added. In Mexico, it usually isn't, and 10-15% is customary.
Waiter
No, la propina no está incluida. Es voluntaria.
noh, lah proh-PEE-nah noh ehs-TAH een-kloo-EE-dah. ehs voh-loon-TAH-ryah.
No, the tip isn't included. It's voluntary.
You
El servicio fue excelente. Quédese con el cambio.
el sehr-VEE-syoh fweh ehk-seh-LEHN-teh. KEH-deh-seh kohn el KAHM-byoh.
The service was excellent. Keep the change.
"Quédese con el cambio" is a common way to tip when paying cash. It's polite and straightforward.
Waiter
Muy amable, muchas gracias. Que le vaya bien.
mooy ah-MAH-bleh, MOO-chahs GRAH-syahs. keh leh VAH-yah byehn.
Very kind, thank you very much. Have a good one.
"Que le vaya bien" is a warm farewell meaning "may it go well for you." You can reply with "Igualmente" (likewise).