There are several good reasons for dormant pruning. Without the leaves present, we can see the entire plant, looking for dead branches, crossing branches and older branches with insect or disease damage. Pruning before any sap flow also means all overwintering energy in the root systems will go to new and existing buds for regrowth and recovery.
You can read books and watch the YouTube videos, yet nothing takes the place of actually getting some "hands on" experience to make you feel comfortable with it. If you already know the plants in the yard, then finding out the best way to prune them is easier. If you are new to the whole yard maintenance scene, then enlist some help in finding out what you have. Even in the winter, fallen leaves at the base of a shrub aid in identification. How buds are arranged on the stem will help too. Shrubs have buds opposite one another or in an alternate arrangement. Twig color also can help. Some shrubs bloom on last year's growth and others on current year growth. This is important to know so you are not pruning away this year's coming bloom show. Taking photos to share with others also can be helpful. Leave them on your phone or carry them with you when visiting garden centers or talking with other gardeners.
If your shrubs are not out of control and are on the younger side, renewal pruning can be done. Renewal pruning is pruning away a percentage of the oldest branches over a 2- to 4-year period. The branches left will be younger, more vigorous and will bloom better for you.
If shrubs have not been pruned for several years or are really old, sometimes it is better to start all over with renovation pruning. This seems drastic in that you prune away every branch leaving just a stub an inch or less at the soil line. This is not for every shrub just because it appears old. Better to find out what kind of a shrub it is first!
In either of the treatments, the first branches removed should be those that are already dead, those causing crossing branches in the canopy and those that have evidence of insects or diseases present. Dead branches are nonproductive to the plant can actually be removed anytime, not just when we do a dormant pruning.
To modify the old carpenter's adage, "Look twice, cut once." For gardeners, at least plants grow back so eventually you have another chance if you prune out the wrong branch!
Richard Hentschel is a Horticulture Extension Educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. Stay tuned to more garden and yard updates with "Down the Garden Path" at go.illinois.edu/downthegardenpath and the "Green Side Up" podcast at go.illinois.edu/GreenSideUp