When students are able to determine the author's purpose of a text, they can better understand the central idea and how details work together to convey the main idea.
Whenever I teach main idea to my students, I try to help them focus on the different types of print that are typically persuasive, informative, and entertaining.
The focus then gets even more microscopic. We then look at the author's purpose for including a specific text detail. This extends beyond persuading, informing, and entertaining.
For an author's purpose game that uses pretend potato chips to review this concept, Click Here