I spent too many years with digital photography before I finally figured out why I was always fighting to get the proper colors during post. I had no clue about white balance. Joining the forum here about 6 months ago set me on the trail. But it was my totally screwing up using auto WB at my my ex-step daughters wedding this past March (as a guest, not paid photographer) that really kicked me in the pants. Hard...REAL HARD.
Fortunately for me, I had switched to RAW+L JPG in my camera (again, based on what I read on this forum) and although I didn't have, and didn't shoot, any grey cards during the wedding, I managed to get 'close enough' WB in Lightroom 3 using the WB tool clicking on white shirts, and touching it up from there.
Since then, I've continued to hone my WB techniques...first with a grey card and now with an X-RITE Color Checker Passport. I'm still 'rough around the edges' in using them, but there's been major leaps in my white balance and color accuracy since then!
So, to be safe, I still shoot RAW + L JPG, and take shots of my Color Checker in each of the lighting conditions I will be in during that shoot. I also set CWB in the camera, as well, when I remember, as I go from one lighting situation to another. My goal, at the moment, is to get acceptable JPG results. That way, I have even less PP touch-up to do. But if I have the time, or I really messed things up color-wise, then I can Lightroom until I drop (if necessary) and get the results I want.