Step 1: Match the Depth
Dig a planting hole that is as deep and twice as wide as the rootball of the shrub (here, a viburnum). Place the plant into the hole and lay a pole across the top to make sure that it is at the same depth as it was in its original container. Adjust the depth of the hole if necessary.
Step 2: Backfill Rootball
Set the shrub in the hole, and then backfill around the rootball with your hands, firming the soil with your heel. At the same time, create a slight saucer-shaped depression within the soil surrounding the plant—this will encourage water to collect naturally over the root area.
Step 3: Water Well
Prune lightly only if necessary: cut out any stems that are dead or unhealthy, and prune any that are growing toward the center of the plant back to a healthy, outward-facing bud or shoot. Water the plant well, and then apply a mulch, making sure that it does not touch the stems.
If you decide that a shrub is in the wrong place, you can simply move it.