Decided on the purpose.

Do you want a pond to be a water feature or a place of wading? Will it be a focal point, part of sanctuary or a private area next to a bench or hammock? Do you want to leave the water clear, or do you want to add fish and aquatic plants? Do you want a still pool that reflects the trees and sky, or do you want to add jets or bubbler heads so that you can create noise and movement?

Decide on the shape and style.

It is very advisable that any hardscape feature needs to relate to the architecture of the house. If your house is formal, a rectangular or round reflecting pool would be more appropriate than a freeform pond surrounded by boulders with a trickling waterfall. Remember that if a pond is far enough away from your house, you have license to experiment with a different and perhaps more rustic style.

Decide on the dimensions—and when in doubt, think big.

A preformed liner in a store can look huge. In your hard, it may be just the opposite. I’ve found that people generally fail to think big enough when it comes to ponds, even if they carefully plot them on paper. This is why it’s important to spread a tarp or take a garden hose and mark where your pond will be. Be sure to view your marked area from many points in your yard—and from first- and second-floor windows that will benefit from a view.

Decide on depth.

Ponds can be shallower than most people think. Two-and-a-half feet is a perfectly good depth. If the pond has a black liner, it will look bottomless. A shallow pond may let you avoid the need for safety fencing, which is required around all swimming pools and ponds of a certain depth. Before you start your design process, be sure to check your local building codes.