Monochrome Fan,
another way of thinking of it is like this:
Whatever you point your (reflected) meter at, it will give you the exposure value that you need to make whatever you're pointing it at middle grey (Zone V) in your negative. It cannot know if whatever you point it at is light, dark, mid grey or whatever - you have to know that. It just tells you the aperture and shutter speed that will result in middle grey for whatever you point it at. Nothing more.
So with a standard reflected meter (say 30 degrees), you will get an average reading of most of your scene usually. In many cases this will be pretty far off, but it will depend on your subject and the overall contrast of the scene. With a spot meter, 1 or 5 degrees, you can find something in your composition that you want to be middle grey - Zone V, and measure that with your meter. Measure something very dark and very light to set your Zone II and VIII (or I and IX if you prefer) and see whether the contrast of the scene fits within the 11 total Zones. If you only have a few zones of contrast (foggy day) you might want to consider expansion (it's in the book, N+1 or N+2), if you have more than 11 (bright sun and lots of contrast) you might want to consider contraction (e.g. N-1).
To make it easy on yourself (what I often do, spot meter or not), point it at the palm of your hand (in shade for negative film, in sunlight for positive) and reduce the given exposure (either aperture or shutter speed) by one stop (Caucasian skin is typically Zone VI). Only works if you're an old white guy
If you have an incident meter (or a dome for your reflected meter, most come with one), even easier is to simply point the dome from the subject (or light that matches how your subject is lit, if it's far away) towards the lens of your camera, and in more cases than not you'll have a perfect exposure. Not always, but most of the time. Again, if you're shooting slides, measure with the meter in the light, if using negative film measure in the shadow. This helps avoid blowing our your highlights on slide film and ensuring enough shadow detail on negative film.
As several other's have pointed out, you may be overthinking things. While Ansel's books are great references, they're not the best place to start if you're just getting into this, they are for when you have a solid foundation and some experience with the camera and in the darkroom. Thankfully negative film is pretty forgiving, and a great way to learn.
Hope this helps!
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