While many species of shrubs are deciduous, which means that their leaves fall off every year, some are evergreen, retaining their leaves year-round. In the majority of instances, by identifying the leaves on these evergreen shrubs you can identify the shrub itself, as many shrubs have similarities in regard to their other features. The color, size and shape of evergreen shrubs are what you need to spotlight when trying to discern one species from another.
Pick up a field guide to trees and shrubs of your particular part of the United States. Study the shrubs in it before going out into the field to see some of the characteristics that evergreen shrub leaves possess. A guide that contains only the shrubs in your region makes things much easier, as you can avoid having to look over those species that may resemble a particular plant but do not grow where you live.
Use the aroma of some evergreen leaves to identify the shrub. One such case is the wax myrtle, which may seem more familiar when it goes by one of its other names, southern bayberry. Wax myrtle has a pleasant odor to it and this scent often shows up in candles, extracted from the berries that the shrub produces. Crush the leaves of a wax myrtle and you will experience this scent.
Look at the appearance of an evergreen shrub leaf and feel it to try to identify it. This works well with evergreens like the rosebay rhododendron, a common evergreen in the East. Look at the leaves and you will see that they seem to shine, reflecting light to make you think they have a coating of wax paper on them. When you feel a rhododendron leaf you will probably come away with the impression that the leaf has a leathery texture.
Distinguish evergreen shrubs by the thickness of the leaves. Many evergreens will have leaves that are more "stout" than deciduous shrubs. One such plant is the Chinese privet, an invasive plant introduced from China. The leaves are much thicker than normal leaves. Once you establish a leaf as having this trait you can center on evergreen species in your field guide.