Tipping isn't as prevalent in Poland as the US and Poles don't tip much themselves but it is widely expected for foreigners to tip in restaurants or bars. A rule of thumb is roughly 10% in appreciation of satisfactory service, 15% if service is excellent. Leave cash on the table or round up the bill, saying "Raeshty nye chaeba" ("Keep the rest"). If you say "Thank you" when you hand over payment that will also be taken as "keep the rest". Tipping in cash is much preferred to adding the tip to a card payment. If you take a tour and are happy with it, you can tip the tour guide if you wish. Taxi drivers don't necessarily expect a tip but if the ride is smooth, speedy and the cabbie makes an effort to converse, you will probably want to tip in the region of 10%.