1. Only writing is writing. Talking about writing isn't writing. Reading isn't writing. Thinking up ideas isn't writing. Only sitting down and writing words counts. There's a quote I've heard attributed to Kingsley Amis that summarizes this nicely: The art of writing is the art of applying the seat of one's trousers to the seat of one's chair.
2. Work every single day. Even if you can only spare a few minutes, spare them every single day. Don't miss one. A novel is a big thing to keep in your head, and you have to build up momentum on it. In reading writer interviews - and I've read a lot - it seems the most consistently productive writers all try and work every single day.
3. Don't worry too much about being perfect. It won't be anyway, so don't drive yourself nuts. A bad finished draft is better than a polished pile of scraps.
4. Don't take yourself too seriously.
5. Exercise. I'm pretty sure this helps you write. But even if it doesn't you may as well be in good shape, right?
Steve Hely is the author of How I Became a Famous Novelist and a writer for The Office, 30 Rock and American Dad. He is a guest of the Melbourne Writers Festival.