Tipping is always a difficult topic, as there are no hard-and-fast rules.
Restaurants: about 5-10 percent of the bill, depending on the level of the service. It is customary to give the tip separately, cash.
Cafes: rounding up is common, but the amount should not be too small. You can leave some cash on the counter, or indicate you don't need to get the change.
Hotels: if the service was good, 5 to 10 Euro is reasonable.
Taxis: upward rounding is usual, or give a few euros extra.
Hairdressers: are not usually tipped, unless they're very cheap.
2 Euro coin