"Correct WB" have 2 meanings, IMHO.
1. Correct as in the pictures appear exactly the way the view is seen on site ;p
I guess there is no way to "make it correct" unless you're doing the post processing at the scene and adjust according to judgment by referring to the surrounding. If you have already left the scene, then it is quite impossible to tell what is the "correct" WB as you see it at the scene, other then by trying to recall.
2. Correct as in "accurate", i.e. white object appears white regardless of the lighting
In this case, it maybe possible to correct WB by PP if there is a white reference but the "correct WB" may not be pleasing at all. For e.g., there is a white object at the scene, and you know it's white, but if during PP you set it as the "white point" (which is correct), the picture may looks terrible.. It may not be exactly like it was seen, esp if the lighting is not white. Because even if the software tries to correct the WB, some colour might already been missing from the picture data that is needed to reproduce what the subject actually looks like under white light.
Inspite of the above comments, if you want some reference for WB correction, you might want to visit the link. Even if the WB is not "correct", it might give acceptable results.
http://www.clubsnap.com/forums/showthread.php?t=482485
A member has provided some very nice WB correction tips..
hi all...
been shooting for a while now..
but i realised that my wb is always off...
is there anyway to make it correct?
i shoot in raw always so i do have the freedom to change the wb..
but the question is, how to see that the wb is right?
any one can help me on this???
thanks!!