The art of topiary, and yes it is indeed an art dates back at least to Roman times. Topiary is the trimming and pruning of trees and shrubs to such a degree that their natural shape is hugely altered. Practiced for centuries and years to learn most people keep their distance at trying it. No one says you have to be an expert, practicing a little topiary here and there can be great fun in your garden.
For topiaries tight low growing shrubs work the best, such as yew, boxwood, holly or privet. With small leaves they provide a dense and richly textured product. Any shape can be produced, you are only limited by your own imagination. You can produce simple shapes such as squares, balls or cones or be more daring and produce a shape depicting a bird, animal or anything else you want. Topiaries also offer the opportunity for humor in the garden setting.
The easiest method to make a topiary is to carve your shape out of a solid shrub. This works very well if you have planted boxwood into large pots. An arrangement of pots with different shapes and sizes of boxwood topiary can be very effective. For larger specimens it is probably better to train the shrubs to the shape you wish as the shrub grows. To accomplish this you use a wood or metal former. The shoots of the shrub are attached to the form and trimmed as they grow until the desired shape has been reached. This form will also act as a guide for trimming once your topiary is completed. Of course, anything of good size will take years to complete. Definitely a project for the patient gardener. Smaller shapes will be completed much faster, such as simple ball or cone shapes. To ensure that sunlight and air will reach all surfaces, it is wise to leave the base wider than the top.
Tools of the trade are sharp clippers and pruners. Unless your project is on a very large scale stay away from powered tools. It is too easy to loose control. For large stems use pruners snipping out one stem at a time. Once you have your basic shape trim using sharp clippers or hedging shears. General maintenance is required to keep things intact.
All sounds a bit daring I know. For a start you can always try out your artistic talents on woody herbs such as lavender or rosemary. You might find this a little less intimidating.