I'm using Lightroom 4, trying to adjust white balance using the eyedropper by the Temp slider, but I'm not sure where in the image to click to get the right balance. I did not use a grey card, so do I just click an area where RGB values are equal? I tried doing that but it seems hit or miss, and it's tough to just find a spot where RGB %'s are equal. Gotta be an easier way...
The correct way to use the white balance dropper is to click on an area that should be a neutral grey, not one that's already grey. So ignore the RGB percentages and look for a something grey in the photo: maybe a stone, a metal surface, some clothing or a shaded white area. (If the white balance is off it won't look grey yet - it might be a bit too yellow or blue, for example - but watch what happens when you click it with the dropper.)
Failing that, other ways to correct the white balance are to choose an appropriate preset from the dropdown list, or tweak the Temperature and Tint sliders by hand. (I always do the latter now - but it depends on how good an eye for colour you have, and it'll help if your monitor is correctly calibrated.)