NB You can get similar forms online to the one we have, but when we investigated all those, we felt they were unnecessarily long and complicated. The one we used is plain, easy to read and understand, and seems to cover everything adequately from a legal point of view.
Let me be clear that I’m talking only of Australia here. Other countries have different laws, so if you think it’s something you want to make a decision about and you live elsewhere in the world, you’ll need to be sure how it’s done there. One thing I do know is that laws on this vary widely, not only from country to country, but often from state to state within a country. I can't even be certain that what I said applies uniformly in all states of Australia.