Juniper – Wilson's Garden Center

Pruning:

Junipers generally need little to no pruning.
They may be pruned anytime except during sub-zero weather. The best time is early spring before new growth.
The best pruning method is to cut individual branches back to an upward-growing side branch.
While shearing is quick and easy, it is not recommended, especially after mid-summer. Shearing creates a dense growth of foliage on the plant’s exterior. This, in turn, shades out the interior growth, and the plant becomes a thin shell of foliage. Frequently sheared plants are more prone to show needle browning and dieback from winter gold and drying winds.
Any pruning that tapers in towards the bottom of the plant will lead to thinning of the lower branches due to shading. To keep the bottom full, the base of the shrub needs to be wider than the top portion.
New growth comes ONLY from the growing tips. Branches cannot be pruned back into wood without needles. If the shrub is pruned back to bare wood, it will have a permanent bare spot.
For shrubs that are getting too large, it is better to prune them back as they begin to overgrow the site. Pruning back of severely overgrown shrubs generally gets into wood without needles. Consider replacing severely overgrown plants with smaller cultivars or other species.

Check out this great pruning fact sheet from Colorado Master Gardener: