Draw a conclusion about which elements were most likely invented by the author, and which are mostly likely historical facts.

If I am not mistaken, we would need more details to answer your question. What author do you need to talk about? Do you need to pick any work of his or her?  Being aware of the writer's purpose when you read helps you evaluate how well the writer has  achieved the purpose and decide whether you want to follow where the writer is trying to lead  you. The active reader reads more than the words and more than even the ideas: the active reader

reads what the writer is doing. The active reader reconstructs the overall design, both the writer's  purpose and the techniques used to realize that purpose.

wow there were a thousand people in the concert. that’s great

depressed people should not argue