If you see green under the bark, the plant is still alive. If you don’t see green, try scratching lower on the branch. If you eventually see green under the bark, you will know that the part above that area was killed by the winter. If you find the green near the top, you can give the plant some fertilizer and see if you can get that damaged root system growing again.
It is not unheard of for a plant to drop those damaged leaves and to put out new leaves. If the damage is partway down the stems, you can prune out the damaged area and give the plant some fertilizer. This will encourage new growth and allow the plant to fill in those spots that were pruned back.
The worst-case scenario is that the plant died over the winter. In this case, you should dig up the plant and replant a new plant. Before you put a new plant in the ground, you should check the soil to make sure that it has enough moisture-holding capacity to prevent the roots from drying out during future dry periods.
In the case of the broadleaf evergreens, you need to be sure not to create a situation where the roots are going to be constantly wet. This can lead to diseases that will kill the roots. Depending on the type of soil you have in your yard, you may need to add compost to the soil or you may need to remove the existing soil and add a mixture of soil that will promote a strong root system.
The other thing that I have found is that in many cases, the plants that were damaged or killed by the winter were plants that were not protected against the winter winds. Many customers told me that they meant to spray the plants with an anti-desiccant spray or they meant to wrap the plants with burlap.