Color Grading Practices Clarified

As I'm beginning to color grade, I'm realising that this process is very, very complicated. I've watched tutorials and taken detailed notes and I'm totally confused. Although I realise that this is a subjective process, part craft and part art, I'm till trying to understand basic guidelines where there's a general consensus about things to do versus avoid.

These are the steps that I've generally found people agree about: 1) Base correct for major issues. 2) Shot-to-shot comparisons between clips to create compatible look. 3) Group clips. 4) Create a look (use a LUT or create your own LUT). Okay, so I'm understanding the broad overview. But I'm struggling with the logistics of the process.

And these are the points of consensus around what not to do: Keep highlights below 100 and shadows above 0. (Okay, I get how to do that by reading levels from a histogram.) And don't oversaturate chroma levels. (Okay, but how do I know when my chroma levels are oversaturated? What does that look like on the scopes or number readouts?)

The following is a summary of some guidelines that Tom suggested.

In the project the process is usually you do luminance adjustment first, always using the scopes. Do a master shot first, not necessarily the widest shot, but representative shots. 

1) Start with the black level, then do white level, and then do mids. Then you can do the white balance using the RGB. 

2) Paradae and adjust the color, the hue and saturation, using the vectorscope (color wheel). You do a base grade for every shot in each scene. Usually shots repeat, like the same closeup recurs, so you copy the grades. Then you adjust adjacent shots in the same scene so the look similar. 

3) Finally, you can add a look to the scene. This is often done with an adjustment layer. 

Maybe a simpler way to phrase this is, What step of the color grading needs to be done to accomplish what stated benefit? What tool is best used in the process? And how does one use the tool: What guidelines for limits on levels, etc?

If I look at the default functions of the FCP color board, I see three options: Color, Saturation, and Exposure. In other words, what am I trying to accomplish with each of these functions (keeping highlights below 100 and shadows above 0, etc?), what is the best sequence (make adjustments to Exposure first, then Saturation, then Color, etc/) and what tool is best used for that purpose (histogram for exposure, vectorscope for color, etc?). I don't know where to begin this is so overwhelming!