I start at the end.
There are two classic ways of approaching writing a novel. In reality everyone discovers their own way of going about writing their novel(s). This way is some version (which probably evolves over time) of one or the other or a mix of both of the classic two. But back to the two classic models: one is known as a pantser (as in by the seat of your pants), and the other is a planner (someone who outlines the whole book before writing the first draft). Pantsers don’t want to know the plot (or maybe even all the characters) before sitting down to write the first draft. They like being surprised and finding the book along the way. Planners want to have it all (or some of it) outlined beforehand, sometimes having outlines as long as ninety pages before setting out to write the first draft.
Before I write my first draft, I need to know what the climax of the novel will be. In fact, the climax is something I must know before deciding to write a book. Because the climax is the purpose of the book. The climax is why I am writing the book. The climax says something about life. You write a book to say something about life to your audience. Something about being a human being on this planet that you want to communicate to your audience. That does not mean that your novel is didactic. Whatever you have to say, you need to say it in an experiential way, not an intellectual way. And when I say something to say, I mean that in the broadest terms. I am writing this book because of this “thing.” I want to communicate and communicate in an experiential way. And the climax is the final word on that “thing”. You may be illustrating that “thing” all the way through your book, but the climax is the final proof.
If Romeo and Juliet didn’t both commit suicide at the end of the play, the meaning of the play would be vastly different. You can’t even imagine Romeo and Juliet with another ending. In the movie Gladiator (the first), Maximus dies at the end. Suppose he had lived. The whole meaning and the power of the picture would be different. Think about your favorite books, movies, and poems, and consider that if the conclusions were different, how would you feel about them?
And so, my writing process starts at the end and then builds up everything that leads up to that ending.