Just as in any other photograph, you need to hold detail and texture in both the shadow and highlight portions of the image. If you follow the gray card rule, you will lose those beautiful subtleties of tone and color that make great snow pictures great, and end up with very little snow detail. As a general rule, when reading off the snow, I follow a sequence of three exposures per composition. When photographing people or animals in snow, the best way to reduce contrast is to use fill flash. This also is a great method to put that all-important highlight in the eye that can make or break animal pictures.
Contrast can be a major problem when photographing people or animals in snow scenes.
This is where a spot meter is very useful. Take a reading directly off the subject and underexpose by .3 stop. If you don't have a spot meter, take a reading off the snow and open up 1 stop. A polarizing filter is good for eliminating reflections from snow. However, you should turn the filter to a medium or low polarizing effect or you will turn the blue sky to a very unnatural looking deep blue.