Inspect the shrub for dead, diseased, damaged foliage and branches. Remove any of these that you find, cutting back to a point of healthy tissue or all of the way down to the crown if necessary.
Trim back healthy branches that have become bare or defoliated with time. Place cuts down to a foot or less above the crown, to spur development of new leaf-covered shoots to fill in what was lost.
Reduce the height and spread of the shrub by pruning back the terminal tips of the longest branches to the desired length, while still maintaining the general natural form of ligustrum. Place all cuts just above a lateral branch or leaf node.