While tipping isn't standard in Australia, I still tip sometimes when the person has done a great job. I have been overseas 3 times. In NYC I once left no tip as I think it was probably the worst service I have ever had, the guy was lazy, we had to ask twice to get water for the table (only 2 people) and then when we needed more we had to ask twice again, the glad of wine ordered at the start came out after mains, even though we ordered starters after the drinks. My bourbon came straight away.
In general in the US we tipped 15% for usual service and 20% for good service. But we also usually rounded the total up to the next dollar as well to keep things easy.

In Thailand, on the way out, we had to get from a hospital, back to our hotel to get our bags, and then to the airport. The driver broke a few laws (speeding, running red lights (after pulling up and seeing that he wouldn't cut anyone off if he went)) he hopped out of the cab to load or bags in at the hotel and at the airport got them out in a hurry too. I tipped him all the Thai baht I had left in my wallet, I was only going to have to exchange it and loose some more in fees. It was a little under 6000baht total that I gave him for a 400baht taxi fare. I didn't want him getting any fines for breaking laws (even if he didn't get any), I knew it would blow his mind, I knew it would help his family (he had a picture of his wife and young daughter on the dash). He said no to it initially and tried to give it back, I said no, he tried to give it back to my SO, she said no. He looked like he was going to cry. I tipped big often in Thailand because I knew small amounts from Australia meant bigger amounts in Thailand.