Snow training is part of the initial part 135 training where I work. We do about 2 hours of ground followed by a flight up into deep snow country to practice the techniques. We also conduct quarterly training, (albeit only 30 to 60 minutes of flight--unless more is needed). We try to make at least one of the quarterly's to be in deep snow.
Here is a brief list of topics we cover...this is off the top of my head as I do not have my training manuals at hand---hope it helps:
Discussion Topics:
1. Weather and wind.
2. High and low reconnaissance, including: ridges, valleys, snow conditions, wind evaluation, slope evaluation and approach/departure corridors..
3. Approach and Landing, including: angle, obstacle avoidance, white out, powder vs. packed ice, flat light, slopes, sliding, settling onto snow, packing down, shutting down.
4. Lift off and departure, including: clearing the skis, start up on ice, white out, TR clearance, departure path choices.