At the recent ACES: The Society for Editing conference, I gave a session on diagramming sentences. It was during the last session period of the conference, on a sunny Florida afternoon, and more than 100 people packed the room to learn, or refresh their memories, about sentence diagramming. (We’re talking about the classic “Reed-Kellogg” method here, not the tree diagrams of great utility to linguists.)
Diagramming has fallen out of favor as a pedagogical tool (it was of questionable effectiveness anyway), and it’s not necessarily something that will make you a better editor. However, it can be helpful to visualize a sentence’s structure, and the “puzzle” aspect of it makes it nerdy fun for many of us who love language. Plus, it’s really easy to spot a dangling participle when you’re diagramming.
The enthusiasm at the conference for diagramming was such that I thought it might be fun to continue the practice, with weekly (ish) “diagramming challenges.” This is the first, and we’ll start simple:

We have a classic subject-verb-object structure here, with modifiers. No compounds, no subordinate clauses. So you have one main line for the main clause, with a few modifiers. The modifiers — an article, an adjective and a prepositional phrase — all go with the direct object, so they all need to drop from that section of the diagram.
“I have a bad feeling about this”:
I hope you had fun with this — we’ll try another one next week!