Well, keep focused on three things:
1) Speed - You need to keep your speed up since the deep snow will be slowing you WAY down. Carry lots of speed across flat spots and stick to the high-side of trails if you can. That way if you wipe out you have enough downhill to get going again.
2) Keep the nose up - If you let the nose of your board go under it could send you into a cartwheel or serious faceplant. To help, shift your weight from center to 60 percent towards the back foot. No this is not typically the proper form for hardpack or groomers, but you need to make this adjustment for the deep stuff.
3) Stay base flat - High edge angles (tipping your board way ob edge) is fun for carving on groomed trails, but could cause you to sink in deep or soft snow. Focus on keeping your board flatter for better floatation.
Now go get ya some!