Provide a location which receives 4 - 6 hours of sunlight per day . Next, consider the size of the pond. Before digging , it is best to measure and determine the size of the pond liner needed. Lay the shape and size with a rope or a garden hose. Check building codes.
Some areas require safety fencing.
After determining the length, width and depth of the pond you can determine the size of the required pond liner. Add this sum to the maximum width and length of finished pond. This is the minimum size of liner material required. Their site has loads of information including a pond calculator for figuring the size liner you need, pump size and filter size. The measurements are U.S. and Metric.