Thankfully someone somewhere had a question that they couldn’t answer and some helpful soul directed the individual to this site:
The Following is a direct quote from his site. I quote it here for my own quick reference and to help you get right to it. PLEASE if you enjoy Ken Rockwell’s site, and want to donate to it click here. If his site can answer some of my other questions as well, I’ll be sure to be donating again.
You use this setting with a white or gray card to get perfect color matching. The D300 can recall five settings: just hold “WB” and spin the front knob after choosing PRE with the rear knob. You can to use menus to save the five settings.
I never use an actual card. I always grab a napkin, t-shirt, back of a menu or other piece of white. Black text makes no difference, so long as the background is white. If you choose a bluish piece of paper (like a glossy printed piece), your results will be warmer (more orange), and if you use a more orange piece of paper (like a cheap paper napkin), your results will be more blue.
Avoid gray items, since they are very rarely neutral, even if they look gray.
To set your white balance to something white:
1.) Ensure your card or other neutral object is in the same sort of light as your subject. Changing the angle of the object often will favor one kind of a light or another in mixed light, which will greatly affect your result.
2.) Hold WB and spin the rear dial to get to PRE.
3.) Release WB.
4.) Press and hold WB again for a few seconds.
5.) PRE starts to blink.
6.) Release the WB button.
7.) Point your D300 at the card and press the shutter.
8.) If the display flashes “good” you’re set.
9.) If the display flashes “ng” then repeat from step 4.)
The D300 stores this as value d-0. You can save five different values using the menus, numbered d-0 through d-4. d-0 is always the value you just saved. You can recall the other saved values by holding WB and spinning the front knob. Thank God you can recall them without menus. The menus (explained later) are only for storing, sorting and managing these. I have mine set to 1.) indoors under crummy residential light, 2.) the screen of my laptop computer, 3.) mercury street lights and 4.) a cloudy day. I’m sure you will be more inventive.
White Balance Trims (fine tuning)
These are critical to getting the photos you want right out of your D300.
I rarely get what I want as set above, and usually need to set my image slightly warmer (more orange or amber (A)).
This is easy, but often overlooked by beginners. All you need to do is look at the image you just made on the LCD. Like it? You’re done. Too cool (blue)? Then hold WB and move the front dial a couple of clicks to about A3 and try again. The more A you add, like A5 or A6, makes the image more orange, and the more blue you add, like B4 or B6, makes it bluer.
**Thank you Ken Rockwell**