Create an outline for your shrub by marking two parallel lines (or curved if you want a curved hedge) down the path you want your hedge to cover. You can use an inverted tip spray paint, or a can that allows you to spray upside down, to mark the line. If you have a straight hedge, you could also drive wooden stakes down into the soil every 4 or 5 feet and tie string around these to create a really visual outline. The two lines should be the same distance apart as the diameter of the shrubs' containers, or the size of each shrub's root ball. This will allow you to visualize the hedge in your landscape and it will give you a planting guideline so your hedge will follow a straight (or uniformly curved) line.