This is just a little test scene experimenting with tracks made in snow (made by a humanoid or car). It’s just a sub-divided mesh, converted to a soft body with high friction (~50) and high edge spring friction (E damp ~ 10). The sphere is set to deflect the mesh, but it could just as easily be the feet of a character.
There are other ways to get the same effect (http://3d-synthesis.com/Displacement_Tutorial.html), but the advantage of this approach is you only need to animate your character and the footprints will follow automatically. The main drawback is to get good footprints you need a heavily subdivided mesh, so what I’m trying to think of is a way to subdivide the mesh over a given radius only where the characters feet make contact with the snow.