Keep your weight back on the saddle (to keep traction on the rear tire). Keep your arms light, and try not to "steer" the bike (if you've ever ridden in sand, it's the same principle). Be in a harder gear than you think you want - keeping the power down is better than trying to spin with a high cadence.
Be prepared to giggle .
Have fun! I LOVE riding in the snow!
SheFly