It really depends on what you are shooting.
I think the video for this product is a great place to start.
PhotoVision Calibration Targets
Watch the video of the 'How to' use the product.
Once you understand that you don't want any loss in data under 0 or over 255 on your histogram things will be easier to understand. Under normal circumstances there will be a peak in the middle sloping down to the 0 and 255 but not an enormous amount of data toward the ends.
Now.... You have a High Key background so you will have some 255+ portion of your histogram. I would shoot your model with your background lights off and see what the histogram looks like. Then shoot with you BG lights on and 1 to 1.5 stops over you main.
If you have already shot the image you can use the elliptical selection tool and select an area of the image and then look at the histogram to see if it is properly exposed. Someone on here explained this or posted a link to this technique. It was called the Facemask Histogram I think. The face being the most important part of a portrait it makes it easy to see if it is exposed properly.
Here is the article.....
Facemask Histogram
I hope this helps someone. The amount of wealth that I continually get from this site is never ending.
Take care,
Jim