In this video, This Old House landscape contractor Roger Cook shows the right way to prune shrubs.
1. Prune shrubs with bypass hand pruners, not electric hedge trimmers.
2. Electric trimmers cut foliage and stems all on the same plane, which causes green growth on the outside but nothing except brown, bare branches on the inside of the shrub.
3. At that point, there's no way to trim back the shrub to control its size because you'll remove all the green foliage.
4. Bypass hand pruners provide a much better, albeit slower, way to prune shrubs.
5. Carefully cut branches just above a bud, which helps a plant heal and grow properly.
6. Prune branches at different depths to create holes into the shrub that let in sunlight. Soon the shrub will be green on the outside and inside.