At the beginning.
Easier said than done, of course.
This is a question that has plagued authors since the dawn of time, and will continue to plague until the end of time. Sometimes a writer will get lucky and know exactly where to start a story. Sometimes, well, not so lucky.
With my last thriller, I was lucky. With my current thriller, not lucky at all.
I've learned, with both projects, why the starting point will elude me at times. It comes down to this - back story versus main story.
Never ever start a story with the back story. Think of it this way. You want to build a house, but first you have to buy the land. Wasting 100+ pages describing that bit of land before building the house, when all readers want to know is the interior of the house, is a glorious waste of time.
Wait! Not all is lost.
Back story is a fundamental aspect of crafting fiction. It's the foundation to build on. So it is important to fully develop the back story even though it's not seen by the reader. (Unless you read a bad book, but let's keep this positive).
Any author knows, we all spend a lot of time and detailed work on developing the back story. It can be too easy to allow the back story to capture my focus and I start to lose sight of the main story. I often joke I need two brains. I'm not really joking.
It can be tricky, but I've learned to balance things out, so that the back story isn't overwhelming nor understated. I can't give one answer for that. I go through the whole story, bit by by, and decide what to keep and what to throw away. It can be tedius but well worth the effort. It's all a part of crafting.
Back to the title of this blog. Where to start? While working on my last thriller, I developed a rather useful skill. I start at the end.
The grand finale with be my main focuse throughout the story, but if I don't at least have a rough idea of one or two possible endings, I can't write the beginning. I need to know where I'll arrive before I can start the journey.
And sometimes, I have to change traveling routes. It just works out that way sometimes.