When I started at my job (toning photos for the local newspaper, I have several years of self-taught Photoshop experience) my boss tried to get me to read a Photoshop basics book he'd gotten from a Photoshop class he took.
I opened it up, and the 1st chapter was:
1. Starting a New Document.
Click on the File menu at the top left of the screen and select New.
This dialogue box gives you the options for starting a new document. It's best to start with a square or rectangular document.
I couldn't read any farther than that!! Square or rectangular!! As opposed to WHAT?? Circular documents? Triangular documents?
I have browsed through that book since then, what a waste of time.
I have finally gotten him to trust me to the point that he has stopped messing with my settings every day. (He used to change my Gray Eyedropper in Levels and Curves to a peachy shade, for setting skin tones.

I prefer to do things by setting the TRUE neutral and then adjusting the saturation to get a perfect skin tone.)