How should you write a journal entry for a son of a nobleman in the 1600s?

Educated young men did write journals back then (as did some educated young women), so the first step would be to create the character. Give him a name that young men had back then, and decide how old he is. What country was he living in? What was his religion? Who was the leader of his country? If he is the son of a nobleman, what is his father's name and does he have other family members? Obviously, a nobleman's family would spend time doing different activities than, let's say, a poor person or a slave, so how does he spend his time? Is he in school, for example?

Give your journal entry some local touches: any good history book will discuss how the different social classes lived in the 1600s. You might also want to invent a conversation your nobleman's son had with somebody famous: the nobles often knew the important members of the clergy, the important people in business, and maybe even a member of the royal family, if the story is taking place in a country which had a monarchy.

In short, find some little historical touches that will demonstrate your knowledge of life back then. But above all, make sure you create some reason for the journal entry: an issue or problem or important event that might have made this young man write in his journal. With a little creativity, you can make your readers feel like they are there, back in the 1600s, listening to this young man as he tells them his story.