This isn't always easy to do. It's a bit like packing for a holiday but you're not sure where the plane is flying you. It's exciting, sure, but you get a bit nervous too, wondering where you're going to land and what you're going to do once you get there.

Eleanor Nilsson writes in her book Writing for Children about an idea she had, taken from an image in a book she read. It was the idea of a woman cleaning the phone box out the front of her house. When I read this I started to think about this woman too, and began to wonder why she was doing that. Then I thought, what if she's cleaning it with a toothbrush? Why would she use a toothbrush? Perhaps she's run out of regular brushes. Maybe she used to work as a janitor for the council and can't stop cleaning stuff, even if she has to use a toothbrush. Perhaps her husband has done something especially bad, and she's using his toothbrush while he's at work but not telling him.

My first two books started with one idea. Almost Wednesday started with one line: "It was the last time I saw her." I still don't know where that line came from, but that's what I wrote. Then I started thinking. Who is it saying that line? Who is "she"? Where are they now, and where is she going? Why isn't she ever coming back? How will the narrator feel about that, especially if he forced her to leave? How will her family feel about him, if he caused her to go? So I started writing, not knowing where it was all leading, and a couple of hours later I had 3,000 words about Charlie and Beck on the beach in a Tasmanian fishing town, arguing as an enormous storm gathered above them. That is where that book began, all from one line, or one idea.

My second novel, Full Moon Racing started with a picture in my head, taken from my memory of travelling overnight in a car and waking up in a strange place. In my mind was a teenage girl, Gunner, riding in her cousin's HQ Holden, on the highway between Sydney and Brisbane. I knew she was leaving home, I knew her cousin was leaving too, but for different reasons, and I knew that it was the middle of the night. That was all I had. So again I started asking questions - why are they leaving, why did they have to go at night, where are they going, who will they meet, how will they change while they're away? I started writing, and some time later I had a story.

There is a risk in writing this way. Sometimes you'll get on a roll and write 10,000 words of wonderful prose, only to realise that it hasn't taken your overall story anywhere good. Don't worry about it - just put it aside and start again from a place you're happy with. You might use that passage again somewhere else, or you might not. Either way it hasn't been wasted. Writing is a lot like music, and practise is just as important to writers as it is to musicians. Don't ever feel that a long passage has been a waste, and don't be frightened to throw it away if doing so will improve the story. Part of editing is being able to be savage with your own work.

I was once asked to write a story by an English teacher. It was one of those "Write about anything you like" exercises, and I went to this teacher and asked him what my subject should be. He gave me the usual "Write about your trip to the beach" answer. That was when I started to think that perhaps I could look at this old lazy idea in a different way. What if I'd never been to the beach? What if I'd grown up on a sheep farm somewhere and had never seen the ocean? Wouldn't that be a bit different from a trip to the beach made by someone who'd been there a hundred times? What would I think of that enormous body of water that people who live on the coast don't seem to think too much about? The result was Seaside, which you can find via my Musings page. The thing is, any idea can be looked at from a different angle or a different point of view to become a new story. Try it some time.

Finally, let me make you a promise. If you think that before you can start writing you have to sit down and completely plot your story from beginning to end, then you'll never finish that story. Or to be more accurate, you'll probably never even start it. Grab an idea, even one that seems a bit dumb, and start writing. Don't be scared of writing rubbish - we've all written rubbish at some time or another, and you can always put it down to practise! But one day you might surprise yourself!