One of the most important things you can do for your lawn in the winter (besides one last fertilization in the late fall) is keeping it clear of debris throughout the season. Keep logs, toys, and any kind of equipment off your lawn, because once snow comes these items can damage the turf, and leave your lawn vulnerable to diseases.
As mentioned in a previous post, a grass’ root system does a lot of growing during the winter months, when the grass blades go dormant. If you feel inclined to mow your lawn in the winter months when there is no snowfall, adjust the height of your mower to a higher setting. A grass’ root system only grows as deep as the grass blades are tall. Keeping your grass longer will mean the roots will grow deeper into the ground, which will mean a healthier lawn in the Spring!
Also, keeping traffic (traffic of the foot kind, though car traffic shouldn’t be on a lawn anyway) off your lawn when its frosted or iced over. Since the grass on your lawn is stiffened and doesn’t have the flexibility of grass in the warm seasons, stepping on it and bending it could cause damage, and depending on the type of grass, the damage could be permanent.