On the Macquarie dictionary site I found the following guide to punctuation and felt this was a worthwhile resource to share with others.
Word Check which can be found on the Australian Dictionary site I maintain, can be quite useful as many possessives and contractions are included, but quite a few of the subtle uses of the apostrophe are not be found in a dictionary.
Keep in mind you need to not only consider the correct usage, but also convention. For example in Melbourne we have a bridge which crosses the Yarra in the city. I've always pronounced the name of the bridge as Princess Bridge. I find when I ask people in Melbourne most people pronounce the name of the bridge the same way. The actual name is Princes Bridge. To me that made no sense. It was only recently that I found out that by convention the apostrophe is not included. Logically it should be Prince's Bridge, but by convention it is Princes Bridge.
We also have a major highway being the Princes Highway. Next time someone mentioned the name listen carefully. Chances are those around you will be calling it Princess Highway as well. Now you know, you may wish to let them in on the secret.