I know this is about tipping or not but, in those places where one would not usually tip, shops, buses etc a nice big thank you would be greatly appreciated and can really make the staffs' day. There are other poorly paid people that you come in contact with where you would never dream of leaving a tip and a little appreciation is always welcome. Only for good service though, I know we all have horror stories to tell.
Here in the USA - I think waitresses/waiters are the only ones who aren't paid at least minimum wage - they are paid - I THINK about half of that - so they have to have tips to survive. It is a system that I don't agree with - however, I always tip at least 20% and sometimes more - so do all of my friends and family - except one cheap family member - I think he still tips 10% - or probably less if no one is looking:)