English Grammar - Punctuation Rules & Writing Tips Here are a few key punctuation rules:1. Use commas to separate items in a list: "I need to buy apples, oranges, and bananas."2. Use a period to end a declarative sentence: "I went to the store."3. Use a question mark to end a question: "Did you go to the store?"4. Use an exclamation mark to show strong emotion: "I can't believe I won!"5. Use apostrophes to show possession or to indicate missing letters: "This is Jane's book." "Can't" instead of