spot metering help needed

I am an advanced amateur, and I want to really understand spot metering 
practically. I've read the "Handheld Metering Guide" and I don't doubt 
that the authors can meter well, but they have shown they can't instruct 
well. Information is neither too advanced or too simple, not enough 
detail and little more than what a sales brochure would give, might be 
helpful in deciding which type of meter to buy but lacking otherwise and 
if you really want to know how i feel about the book : )

Has anyone read a really good book on metering with great practical 
tips? Where to point the spot etc. I know that sounds like a simple 
question but lets say you are in a meadow in autumn, what element is 
likely to most closely resemble 18% gray.Is that the best approcah to 
find a 18% grey in the scene and meter that? Or do I determine what will 
be grey if I can't control developing and printing. Does the Zone system 
 have use for the digital or roll film photographer?