According to Les Edgerton, who wrote HOOKED:
It's imperative that you understand what stories always have to be about.
One thing and only one thing: TROUBLE.
That's it. Period. There is simply no reason for a story to ever exist unless it's about TROUBLE.
So your story shouldn't begin at any other time than when the trouble really begins. The story doesn't exist before that point.
Hmm...so why do writers continue to struggle with beginnings? Maybe we have to ask ourselves a couple of questions first.
Edgerton says, in your opening scene (the first 1-3 pages), an inciting incident creates trouble in the form of the initial surface problem, which then leads to the deeper story-worthy problems revealed throughout the novel.
The protagonist's world alters profoundly by some event-not material or surface things. Instead, the character's inner psychological world significantly changes for the worst.
That's where your story starts!