Final answer:
Start analyzing an informational text by previewing its structure to grasp how it's organized, which helps identify the central idea and author's purpose.
Step-by-step explanation:
When analyzing an informational text, the first step you should take is to preview the text to understand its structure. This preliminary survey of the text involves a cursory glance at headings, subheadings, introductory paragraphs, summary conclusions, and any other structural elements that can give you a sense of how the information is organized. By doing so, you establish a framework that will help you to identify the central idea, the author's purpose, and how well the argument or information is presented and supported throughout the text.