In restaurants and cafes it’s customary to tip about 10% of the bill for decent service. An interesting note: when your server is taking your bill with payment away, saying ‘gracias’ usually implies that the server should keep the change as a tip. If you want change back, don’t say ‘gracias’ – say ‘cambio, por favor’ instead.
Note that tips can’t be added to credit-card bills, so carry cash for this purpose. Also note that the cubierto that some restaurants charge is not a tip; it's a sort of 'cover charge' for the use of utensils and bread.
Bartenders They don’t expect a tip, but it's OK to give a few pesos for a drink or good cocktail.
Bus porters A few pesos.
Delivery persons A few pesos.
Hotel cleaning staff A few small bills per day (only at fine, upscale hotels).
Hotel porter A few pesos.
Restaurant servers 10%; 15% for fine restaurants with great service.
Taxi drivers No tip unless they help with luggage; many people round up to nearest peso.
Tour guides 10% to 15%.