While many people prune shrubs for the overall health of the plant, many gardeners also prune their spruce shrubs to keep them looking attractive and from looking overgrown. While evergreens such as blue spruce don't require extensive pruning -- the plant doesn't grow continuously and doesn't require much maintenance -- it's best to prune blue spruce in the later winter months before the shrub's growing season. Avoid pruning during the wet or warm season to limit the likelihood of diseases.
Remove shrub branches that interfere with the overall look you desire, but follow the natural shape of the plant when shaping it. Don't force a spreading shrub into something more conical. Remove branches all the way back to where there are needles; never cut back to a bare branch.
Cut back diseased branch areas 4 to 6 inches below the cancerous areas, until you see white wood. If necessary, prune the branch all the way back to the trunk.
Remove some of the inner, upper branches to allow plenty of light and airflow into the center of the plant. Leaving too many internal branches prevents proper growth. Don't just trim the outside foliage.
Remove any other leaders or branches so that there is one main trunk on your shrub.