Tipping in Austria is unlike in the States. Tipping in Florida is 10% of your total at a resturant and at a coffee shop the change given back goes into the tip jar. Waiters and Waitresses normally are paid lower than minimum wage and live off their tips.
When I was living in the States I worked at a local smoothie bar and I know tips were what really made working with all the rude people easier and helped with the wages I was paid. I could right a whole post on how you are supposed to act around a tipping jar because after working at the smoothie bar for a year I saw some people that did not know what was proper. For example we had a few people steal our tips, we even had people search in the tip jar for the change when a order was 3.25 they would thumb around looking for the 25 cents.
I believe Tips should not suppliment a low wage but rather reflect on the service itself. If that person went out of their way for you and was not rude then tipping is easy.
When I was in France tipping was included with the price which made everything you just had to add up your bill and no exactly what it is you had to pay.
What is custom in one European Country is not in another. Here tipping is called "Trinkgeld" which means drinking money *literaly* so unlike the States it not always 10% but it can be spare change and or 2 to 3 euros. And this is not at your local coffee shop but I mean even in resturants that is an acceptable amount for a tip. Now please use some common sense and if you have racked up a high bill and a table of 4 or more please don't tip 3 euros. The higher the bill the larger the tip, but that is up to your own discretion. Always tipping is a good habit, but if you feel the service was poor and the waiter cocked an attitude then you don't need to feel obligated to give him anything.
In Austria when paying for the most part the waiter or waitress will pull out a big black pouch and that is the cash register. Every waiter will be wearing one, and after recieving your bill they will stand right beside you with pouches open waiting for you to pay right then and there. So you have to be quick on your feet on what you will leave because if your total is 5.50 euros and you have a 10 you can tell them 6 and they will hand you back 4 euros. Leaving the money on the table is not customary but if you don't speak the language, you can always wait for them to give you back the change and then hand them what ever you see fit as a tip.