In restaurants, tip up to 10% of the bill if you are happy with the service and food you received.
In bars and cafes, tip up to 10% of the bill. If you only have a coffee or a drink, then leave a few coins as a gesture.
Taxis don't expect tips but do appreciate them. It's polite to round up fares to the nearest euro as drivers often run out of change.
Guides and drivers appreciate tips at the end of excursions, but they are not required. The same goes for cleaning ladies in apartments and bungalows.
Please note that the 7% IGIC charge added to most restaurant and bar bills in Gran Canaria is the equivalent of VAT and has nothing to do with a service charge. Most restaurants now quote prices without IGIC so that they can keep menu prices lower.
Apart from IGIC, there should be no other supplement on your bill although most places add a euro or two for the bread.