I have to admit, have never thought of using this technique before. But a buddy from Gilbert Arizona swears by this method, so I had to try it out. And it works!
1. add a new curves adjustment layer
2. select your white point dropper (third one down)
3. Slide your black point slider to the right to just reveal whites
4. Slide back to normal position and click your dropper in that whitest area
5 Select your black point dropper (1st one on top)
6. Slide your white point slider to the right so just the blackest part of images is apparent. Slide back to normal position.
7. Click this darkest point with a black dropper
You now have a balance between whites and blacks
Curves give you a little more adjustment control of tones. Once your WB is set in curves you can grab individual curves to adjust even further, making it warm, cooler, etc.
*some older versions of CS you have to check box to reveal clipping
*if you don’t want to use sliders in CS/CC click your picker, example white, and press option on mac should be alt on PC to reveal clipping.
There are a lot of different ways to do this process as well, and if you have a technique that you prefer, we’d love to hear about it!