I feel guilty asking this because I am a professional photographer. I'll ask anyways and put aside my pride for the sake of learning from my mistake...
I did a wedding a while back, and I found myself in a situation where I was shooting into the sun and I had a group of 9 people walking towards me but didn't quite know how to find a proper exposure setting. It was an awkward situation where I had to pause the shoot for about 3 minutes because all the adjusting and chimping I was doing revealed a seemingly never ending sequence of over-exposed pictures. (all in manual mode)
This may be where I went wrong... I went up to to one of the groomsmen, I metered his jacket (black) and took the group picture, only to discover I was severely overexposed. After failed attempt over failed attempt, I finally gave in and found a setting that worked in AV mode (i metered the entire scene, it revealed a 4x faster shutter speed that I was using).
Was my mistake in metering the groomsmen's BLACK coat? I'm certain it is, but what should I have metered? The cement ground (shaded) which was a closer 18% grey? Or perhaps the bride's white dress? I'm guessing the ground, but I want to be absolutely certain as I don't want to be in an embarrassing situation like that ever again!