The first pages are a promise, not a preface

Readers decide early. They are not obliged to wait for chapter three, where you have hidden the good part. The first pages have to do two jobs at once: begin a world, and raise a question the reader would rather not put down. Atmosphere alone is not a question. A question has a person and a pressure.

Start as late as you can. The morning routine, the journey to the place where the story starts, the history of the town: these are often the writer clearing their throat. Begin on the day that is different. You can teach us the routine later, in contrast, once we care why it broke.

Plant the want, even if the character would deny it. A person who wants nothing gives the reader nothing to hope or fear. They may want the wrong thing. They may want a small thing — to get through the lunch without being asked about the letter. Small wants are enough if something is already threatening them.

Voice has to be present in the first paragraph, not introduced once the plot gets going. The particular notice — what you mention, what you joke about, what you refuse to explain — is how a reader recognises that this book will not sound like the last one. A neutral opening is a door with no handle.

When you revise, cut the first page and see if the second page is a better door. Often it is. The first page was you working up the courage, and courage can be edited out once the scene is brave enough to stand without it.