Color correction help, this is driving me insane....

I have tried endlessly with color correcting photos. What am I looking for when I'm placing my color sample? For example, I open up a photo. I look around, choose a grey area, at 3x3 or 5x5 average sample. I shift click my eyedropper there. I open up curves, choose the red channel, make the output values the same as green. I do the same with blue, yet my photo does NOT look color corrected. If I open up a photo with too much green or blue, how are people restoring them to regular color? Any help is appreciated, thanks.

http://lmgtfy.com/?q=Color+correcting+photos.