How you plant a hedge depends on the effect you want and how fast you want it.  Use the trench method if the hedge will be lined up straight and plants set close together.  The staggered row is good if there is space for a wider hedge or if you want a screen more quickly.

The staggered row approach can help disguise an unsightly wire mesh fence.  Plant a row on each side and soon the fence is covered.

For easy pruning, a formal hedge demands a width almost equal to its height.  The actual width of the hedge might be equal to half the height, but you'll want an extra foot or so of space on either side to maneuver around.