In Europe tipping is generally much less expected than in the U.S. A good rule of thumb for your travels: forget the American 20% standard. In Spain, Italy, Greece, and Turkey, rounding up or leaving about 5-10% for genuinely good service is usually plenty Here's a practical guide:

Country Restaurant Tipping General Rule
Spain Optional. Leave small change or round up. For excellent service, 5-10% is generous. Not expected, but appreciated.
Italy Optional. Many restaurants charge a coperto (cover charge) or service charge. A few euros or rounding up is common. Check the bill before adding anything.
Greece Customary but modest. Around 5-10% for good service, or leave a few euros. Appreciated, not mandatory.
Turkey More common than in much of Europe. About 10% in restaurants for good service is typical. Service staff often expect a modest tip.

For taxis: In all four countries, simply rounding up the fare is usually sufficient.

For hotels: €1-2 (or local equivalent) for porters or housekeeping is appreciated but not obligatory.