As with all new hedging, Prunus laurocerasus (or Cherry Laurel or Common Laurel) needs some formative pruning to make it as dense as possible. Unlike a number of hedge plants however, Cherry Laurel is almost infinitely forgiving of mistakes, so it is hard not to produce a good hedge ultimately.
In terms of pruning, do nothing.Laurel is an evergreen and as such it is never truly dormant although activity in colder months is slow. Trimming the plants too soon means that the wounds will bleed without the roots having had time to establish and "drive" the plant. Infection is more likely as a result and damage from frost is more of a risk to newly cut tissue than plant bark.
Once Prunus laurocerasus has established (easy to tell because you will see new, young leaves appearing) step back and take a look at the plant. Cherry Laurel will put out new growth from the junction of stem and leaf if encouraged. If you want new growth in a particular area just cut a branch in that part of the plant back so two or three leaves remain. A new side shoot will come from each leaf within a few weeks. Keep doing this until there is a good structure of branches sufficient to carry the canopy of leaves that make common laurel such a good hedge plant.
Once that is done, all that is needed is to keep the hedge in shape.If you have the time, this is best done by cutting back individual branches with secateurs - the leaves of Prunus laurocerasus are very large and hedge trimmers can leave them ragged.This is not a real problem as laurel grows new foliage quickly. Remenber to prune your laurel hedge into an upright "A" shape. A slight taper to a hedge - wider at the bottom than at the top - allows light and air to to get to the lower branches, keeping them healthy and covered in leaf.
To radically change the shape of an established laurel hedge - significantly reducing the height or perhaps making an arch to walk through, mid-winter is the best time for ferocious surgery. You can be brutal however, laurel cut to the ground will just grow back....
If you are tempted to why not take a look at our selection of bareroot Cherry Laurel hedge plants for planting between November and March.