Tipping is a tradition that makes gastronomic workers happy, although tourists are not very pleased. In Greece there is a culture of tipping so if you visit this country in the summer you should count these small but constant expenses in your budget.
In terms of tourist restaurants you should consider following or being aware of certain steps. First things first: ask for the bill. Nobody usually brings the bill if you don't ask for it, so once you have it in your hands you should check it because there may be errors in the orders. If the error is less you can ignore it, if it is not the time to make the pertinent observations. You must, too, confirm if service charges have been collected.
If so, you can already pay the bill. If the attention has been good you can leave a 10% to the waiter but if it has not pleased you, do not leave any extra. Waiters usually share some income. If the owner of the restaurant or tavern has attended you, you should not leave a tip. The tip is always and only for the employed worker. And if the service has not been good or bad then leave the same tip because mainly in season many young boys and girls work basically with tips. A euro or two is enough.
If you sat in a more traditional site, not touristy The procedure is more or less similar: you ask for the bill, you check for errors because it is certain that you have not been charged the service charges. The tip in these types of places is 10 or 20% of the total and you leave it on the table or give it directly to the waiter. Then you say hello and leave. If the tip is to the taxi driver, for the suitcases, there is an official rate because tips are not customary.
And finally in the case of use of public toilets where there are people who provide you with paper and other things, the usual thing is to leave about 50 cents of a euro or one euro.