For those that will remain out in the elements, empty the pots of soil and then cover them to prevent them from filling with water which will lead to freezing and cracking.  If you want to be decorative, tin, copper, stainless steel or aluminum covers can be used.  Otherwise, less expensive exterior-grade plywood works just as well.  Or if they are not too heavy, just turn them upside down.

If you will be storing terra-cotta pots inside, they need to be properly disinfected to eliminate any soil residue that could be harmful to new plantings and vulnerable seedlings next year. Scrub the insides and outsides with room temperature water and a stiff brush. Make sure the pots dry completely before storing to prevent mold and mildew which can be dangerous.

Evergreens, Yews and Rhododendrons can become brown and look burned due to winter weather damage. One way you can protect your evergreens is by staking burlap around the plant to shield it from wind and sun. Alternatively, use an antidessicant spray in the fall which will seal the needles so moisture cannot escape as rapidly during winter.

Another problem is icy tree limbs. Try to keep heavy snow off your fragile tree limbs by using a broom to sweep it off. When the limbs get icy, just wait until the temperatures rise.

For smaller plants, cover with a bucket or a triangle to act as a shelter. Larger plants can be pruned vertically to keep heavy snow and ice they catch. Remove weak limbs likely to break to reduce stress on the tree.