We like the European model that is used in many countries we've traveled to: Service charge is already included in the prices and you do not tip because the servers/waiters are already paid a good wage and don't depend on tips. If you feel you had exceptional service you can round up. For example, if your bill was 47 Euros and you thought the service was excellent you round up to 50 Euros and leave them a 3 Euro tip (or even just a Euro or two is a nice gesture.) Makes life so much easier for everyone.
In Aurba, if there is a 15% service charge added already we will tip another 5-10% for good service but no more than that.