– Use the right tool.
Most shrubs should be pruned by hand with hand pruners. For example largely evergreens like Mt. Laurel and rhododendrons always done with him hand pruners. Shrubs or hedges such as hemlock,boxwoods and yews can be pruned with either hand shears or gas shears. but Shears should never be used on larger leave evergreens.
– When is the proper time to prune?

The best time to prune is after your shrubs have flowered if they are flowering shrubs such as rhododendron in Mount Laurel.this way you are not removing next year’s new flowers. Some plants such as Boxwood may require two prunings per year to keep them in good form.

– To sum up.
If you want your shrubs to look natural hand pruner are the way to go. If you’re looking to make Roundball and square boxes throw out the hand pruners and buy some gas shears.
– Mother nature always wins.
Whether you prune your shrubs yourself or have it done professionally over a 20 year period of time the shrubs are still getting bigger despite your best or the professionals best effort after 20 years chances are the shrubs in front of your house have overgrown their usefulness and need to be ripped out and start over again. You should not feel bad about this you’ve done the best you can for 20 years but mother nature always wins.