Ha! We always tip 20% as a baseline regardless of our location on the planet. I have always been puzzled by people who ask how much to tip their waitstaff in foreign countries. Are they worried they will tip too much?
My guess is that they worry that they will tip too little.
As an aside; we were in Switzerland a few years back. On our first night, we had dinner at a very nice restaurant, had exceptional service and paid in cash with a generous tip included. We left the payment in the folder on the table and walked out. The waiter came flying out behind us, yelling for us to stop! "Wait, wait! It is too much Sir Monsieur Signore Herr!" We tried to explain that in our culture that this is normal but he was having none of it. As a professional waiter, he was paid well and was insulted that we thought he needed more money for doing his job. He demanded that we take the money back. We didn't tip for the rest of the week there knowing that it is not customary.
Hilarious! We are also consistent 20% tippers, wherever we go. And a little tip, when out at a bar, ALWAYS tip BIG on the FIRST drink...not the last or when settling a bill...the pay-off is usually extra special attention from the barkeep, specially in a crowded venue.
Bribing bartender attention is not cool. Other patrons know exactly what you are doing and will hate you for it. Just tip according to local customs and roll with having to wait a little if it's busy. Chat with your bar mates. Have a few laughs. You're on vacation. Relax. Your drink is coming.