Open with a hook line, introduce the main character and what they want, show what stands in the way, and end on the question the book answers, without spoiling it. Keep paragraphs short; most readers see only the first few lines.
Non-fiction
Lead with the reader's problem and the result the book helps them reach. Then list what's inside.
KDP's rules change from time to time. Check KDP's own help pages for the current requirements before you publish.