Curvemeister Forum

I just do what the guideline told me. I set highlight point on the white area near the door and chose RGB.

One question is that when setting highlight or shadow points, should I must choose neutral objects only (e.g. white or black)?

The closer you are to a neutral the less color shift you introduce when you use RGB. 
In LAB the highlight and shadow are independent of color. 

In your image you could use a bit more contrast.  Try to steepen the curve of the RGB combined graph by moving the end points closer to the center of the graph.

when you place the mouse in the upper right corner the cursor will change to a pair of circle arrows.  Move the double circle arrows to the center and the graph will pivot...

Greg