The wall and the post weren't too far apart, and I stood back enough to be able to play with the zoom and focused mainly on the post.

You'll learn pretty quickly how just aperture affects a photo, in how much depth of field you have. The part that's more nuanced is figuring how zoom plays into that as well. Zoom also compresses the depth in a shot, so to speak. The most extreme version you'll see is towns with mountains towering above them that seem like they're in the back yard, but there's really a ton of distance. It just looks almost flat because the photographer is using a really long lens.

There are apps/calculators that will give you the depth of field for any given focal length and aperture, but I found it to be a lot of trial and error when learning how the various settings work together.