Starting a story is like playing fetch. Stay with me now. Picture a nice dog. The nice dog wants to play fetch. You have a stick. The dog is vibrating with eagerness. Do you say:
"Look here, dog. This is a stick. It is fourteen inches long. It's from the neighbor's larch. It has a diameter of three-quarters of an inch at the proximal end, which is held by me in my dominant hand, and half an inch at the distal end, which is pointing at you. There is a slight bend..."
By now said dog has hopefully sunk his teeth into your leg. The dog wants none of that. He does not want you to finish describing the stick and begin elaborating the rules for fetch. The dog does not speak English, but even if he did, he wants none of that information. What the dog wants is to chase the stick. He wants you to throw it into the distance, possibly into a nice pond, and he wants to run after it as fast as he can. He will start running before either one of you knows exactly where the stick will land.
That's your reader at the start of your story. He or she does not want or need to know about the stick or the rules of the game. Your reader just wants to run. He or she will follow your story wherever it goes.
So long as it goes,
And goes fast,
Into the unknown.