Calibration settings are influenced by the projector's environment. What works for one person's setup may not be ideal for yours. The best way is to use a setup DVD that takes you through the settings, one by one, to optimize the projector for your use. Lacking that, then you're left with you own eyeball for what looks right.
To put it in a nutshell, the Brightness controls the Black level and the Contrast controls the White level. With a grey scale, you would adjust the Brightness until the last, darkest black square in the scale is defined from the adjacent square and the Contrast adjusted for the same result on the last White square. Then you get into Color Hue and Saturation and without a the setup DVD, you're pretty much doing to taste.
The point with the Brightness or Black level is to have the right level so the details in the shadows or dark areas are not lost and and the Contrast or White level so images do not "Bloom" from being overdriven.
Having said all this, I'm sure someone will pop in with their "ideal" settings, if you use those and they work for you, fine. But I would treat them as a starting point.