Pruning ornamental evergreens on a regular basis, once a year during their dormant period, is critical to encouraging new growth, which allows the plant to rejuvenate itself. It also can minimize the danger of limbs growing into power lines or getting old and brittle and breaking off, potentially injuring someone. Pruning ornamental evergreens also has a third plus: maintaining the tree's desired shape.
Dip your pruning shears in a mixture of common household bleach and water (one part bleach to nine parts water) to sanitize them. Leave them in the mixture for a minute or two, and then rinse thoroughly and dry with a rag.
Remove dead or diseased branches. Look for discoloration or brown needles or leaves. Cut the dead branches at a downward angle, just outside what's known as a "branch collar," the swollen lump where the branch meets the main stem.
Remove any branches that rub against each other or cross other branches to thin them out. Look for branches that go in different directions than other branches and remove them.
Cut off any vertical shoots. Vertical shoots could develop into parallel stems or trunks, which you don't want. You want a strong trunk ringed by lateral branches.
Shape the tree by pinching off side shoots. This also will result in denser, fuller growth, so your tree won't look scraggly.