Starting a novel is the fun part.

All you have to do is decide what your characters want, and the challenges they need to overcome to get it. The plot, in other words.

Then keep playing until it sounds real. Make the story and the voice so true that when you’re writing, you’re not being ‘creative’, you’re just reporting things that really happened to people you know inside and out, in the most compelling, interesting and charming way possible. You want people to read one page and think ‘I need to know what happens next’. Every line invites them in and makes them feel so comforted and understood that they’ll never want to leave. A good novel is the world’s best hostess.

Next, you have to finish it.

And that’s the tricky part.

Many of us stall about two-thirds of the way into our novels. Your characters have overcome their initial obstacle, but simply giving them their objective now seems too easy. You can’t give it to them and then give them a new, tougher objective, that’s silly. You can’t change their objective completely half way through the story, that’s confusing and unsatisfying to readers. But you need to do something.

So, because you don’t know what that something is, you’re avoiding your novel like an ex-boyfriend at a party. You’re looking out the window and thinking about how nice Ben Affleck and Jennifer Garner seem. You’re trying out all those Nutella recipes everyone keeps talking about. You’re online shopping for a bikini for your next vacation. In eight months.

And you’re here, reading about writing.

Instead of actually, you know, writing.

My friends, I have the answer. Well, answers. It’s a two-part approach. (And just quickly, a caveat: this is just how I do it, and everyone is different, and no one really knows what they’re doing in writing or indeed in life, it’s all about intelligent intuition aka ‘winging it’. So do feel free to ignore me.)

Step 1. Astonish me.

A disaster. A fire. A flood. A storm. A car crash. A discovery. An affair. A hidden past. A secret child. An overdose. An inheritance. A bankruptcy. Throw something new into your manuscript, something dramatic, something surprising that shakes your story and your characters up.

Your characters, with everything else that you’ve thrown at them, will have to deal with that something, making their original objective seem very far away (the ‘all is lost!’ moment).

Then, after you’ve dealt with this event, you’ll find that their original stories and crises will get pushed along to just the right spot so you can – boom! – end it.

It’s tempting to introduce a new ‘central’ character to do something astonishing, but I’d recommend against it. It’s too confusing, and if that character ends up being very interesting and hilarious (and the ones you don’t want to be always are) they’ll take over the story and throw the manuscript off-balance completely.

So that’s the technical answer about what to do.

Now, the hard part: how to write when it feels like homework.

2. Sit down. 

Remind yourself, every day, that writing is not homework.

Writing is your job.

Even if you’re doing something else to earn money (I was a copywriter in advertising from 9am to 6pm while writing my first two novels), if you want to be a published author, then this is your job. You need to turn up every day, at the same time, and get to work. (Take a moment to high five yourself. You have an awesome job.)

Once you’re sitting down, don’t do anything else. Don’t tweet. Don’t blog. Don’t Pin. Don’t go on Facebook. Don’t read. Don’t watch TV. Don’t cook. Don’t make social plans. Just turn everything off, throw something unexpected into your manuscript and stay there till your characters have dealt with it.

I know, it’s hard. It’s exhausting, mentally and emotionally. It’s intense and all-consuming. You’ll be a hermit for at least a few hours every single day. (The only people I see during that stage are my husband and my baby, and the wonderful sitter who enables me to be a hermit without neglecting said baby.)

But it’s also joyful. When you’re excited about writing what happens next, you know you’re onto a good thing. Sometimes you’ll need to push and push your words, sentence by sentence, paragraph by paragraph, till you reach the moment when you can see, quite clearly, all the way to the end of the story. And then, like magic, finishing your novel will suddenly be… easy.

Afterwards you can go out for a walk and look at the blue sky and the sunshine and the people all around you, and think to yourself, I created a whole world in a book, all by myself. How about that.

Good luck. You can do it.

PS: I should tell you that I didn’t apply the Astonish Me approach in my first novel, The Dating Detox, which is a romantic comedy story about a girl avoiding love. I only managed to finish that novel, actually, because I had an enquiry from an agent after just three chapters and a vague synopsis. I was so scared of the agent forgetting me that I slept five hours a night, improvised the plot as I went along, and finished the entire thing in five weeks. So that’s another way to finish a novel: 3. Be Really Scared And Have a Deadline. However, I did apply the Astonish Me approach in my second novel, A Girl Like You, a romantic comedy in which the heroine discovers all kinds of nasty surprises in the third act. And I applied the Astonish Me approach in my upcoming New Adult novels, the BROOKLYN GIRLS series, out July 2013. If you’d like to win one of three copies of the galleys of BROOKLYN GIRLS - (before anyone else gets a copy! Even my mother!), courtesy of my publisher St Martins Press, just leave a comment here. (Be nice!) (Please.) We'll pick the three winners at random by Friday 22 February.