Hedges, not individual shrubs need shearing. Reaching into the plant with a pair of pruners will give amazing results. You will know you've done it properly when the only thing noticeably different about the plant is that it is a few inches shorter all over. There will be no obvious cut stubs showing above the foliage, and the plant will have a natural form. Tree pruning starts getting more exacting.
Trees are a long-term investment, and pruning mistakes can severely shorten a tree's useful life.
To avoid the need to prune young trees, start out at the nursery and buy with a well-shaped specimen. Avoid a tree with limbs coming from the trunk at less than about a 45-degree angle. Choose a tree with main branches evenly spaced around the trunk and along the trunk. Avoid trees with branches all on one side or crowded together on the trunk. When you plant the tree, prune only to remove broken stems.