20D Custom White Balance?

[wklain]

Hey there. I'm wondering if anyone can elucidate upon the Canon 20D's custom white balance function. My problem is simple. I'm sure the answer is obvious. Hence, my many problems. The custom white balance function calls for us to take a pic of a gray/white card/object that is illuminated by whatever light source we'll be using -- be it the sun's rays or a flourescent bulb. Then, we're supposed to set the white balance to manual, scroll to custom white balance in the menu and pick the photo we previously shot (of the gray/white object) under the same lighting conditions. The camera should be ready to find true white. Now, my problem is this. In which "white balance setting" do I take that initial, "reference" shot. The 20D manual says to just pick one. They all achieve different results. My best photos come after using the manual color temperature setting to take the "reference" shot. What do we think? Is there a simple answer? Please. And thanks in advance for any and all help.