First, you need to think carefully about where you will place the pond. If the site has trees overhanging, you will be driven mad by leaves falling into the pond. In a small stretch of water they will cause serious problems, as eventually they will sink to the bottom and foul the water, making conditions unsuitable for wildlife. To overcome the problem it will require a constant effort to clear away fallen leaves, and a lot of time frequently cleaning out the pond.

Don't site your pond in full sun; partial shade is best. A pond that sits in bright sunlight for most of the day does not provide shelter from the sun for fish or other pond life. If the site is too shady, the plants won't flourish (water lilies and other water plants prefer plenty of sunshine). Avoid hollows or low-lying areas. They may seem a natural choice but in heavy rain a low-lying pond will act as a drain for the rest of the garden. This could pollute the water and may even cause the pond to flood. Choose a sheltered site, especially if you intend to have a fountain. In strong winds, water will blow from the fountain lowering the level of the pond.

Next you must decide the size and shape of the pond. The shape can be either formal with symmetrical lines, either square, rectangular, oval or round. The shape of the pond will depend very much on the garden design. Normally the formal pool fits into a landscape that has straight paths, clipped and manicured bushes and shrubs, and an overall balanced type of planting. Informal pools are more natural looking; they are usually irregular and random in shape with curves that enfold them into the surrounding landscape.

Next you must decide which material your pond will be constructed from. A pre-formed pool formed in glass fibre or reinforced plastic are easily installed. The more rigid types tend to be more durable and come in a greater variety of shapes and sizes. The main drawback being that size is limited. If you buy a pre-formed pool, then be aware that however big it looks standing up at the garden centre, it will look half the size when in the ground. Many pre-forms are not deep enough to successfully over-winter your fish, especially in northern areas. Koi because of their eventual size, require a depth of at least 6 ft (1.8m) if they are to thrive.

In southern areas the water in shallow pools can get overly hot, and in winter they may easily completely freeze up. Besides shallow waters allow for fast, fluctuating temperature changes, which can be eventually fatal for fish. Care should be taken to ensure that the pond remains level by keeping a carpenter's level on the pond edge at all times while filling. If the pond moves and the level is affected, stop filling, and relevel, backfilling with sand or soil.