You may have tried to cover plants with sheets, overturned plastic pots, or a thick layer of pine straw. This works well by holding some of the heat that builds up in the soil, and also insulating against cold winds. Some damage may still occur, but less than you would have otherwise.
For those plants that were exposed, scout around over the next couple of weeks to look for damage. Freeze damage on woody plants is usually seen as leaf browning and then leaf drop, or a blackening of a portion of the stem. Perennials show leaves that are droopy and seem to be almost white. I believe most of our perennials that were damaged will resprout with new leaves.
Regardless of the symptoms of freeze damage, all pruning of affected parts of woody plants should be delayed until after the danger of frost is past. Not only is there increased risk of infection when pruning before then, but the old plant material provides protection to areas lower on the plant which may not have been affected. When pruning freeze damage from a plant, prune back to healthy tissue.