1. You can dig it
Look for a spot where there is soil that's not too hard to dig. You will need one or two shovels and maybe a wheelbarrow. If the spot where you want the pond is reasonably flat, you don't even need the wheelbarrow, because the dirt you remove in digging a hole for the pond can be used to build a hill for a waterfall.
2. Ace of spades
Use a round-point shovel to do the major part of the digging. This spade has two curved edges that meet in a point at the tip. The shape is perfect for cutting into moist soil. Use a flat garden shovel with a straight edge for trimming and creating platforms within the pond.
3. Damp is good
If you're lucky enough to have a sandy clay soil, you'll find it easier to dig if the soil is damp. Some clay soils get very sticky when they're too wet, and the clay sticks to the shovel. You'll have to experiment to find the best soil moisture conditions for digging. If you need to add water, use a sprinkler to get it right.
4. Deep thoughts
Many garden ponds are 18 to 24 inches deep at the deepest part. The depth of the pond will depend on what you want to have in it. If you want water lilies and other aquatic plants, you need to plan the pond so the plants are at the proper depth.
5. Rocks roll
Some ponds have shelves or flat ledges on the sides as you shape them. These shelves can have shallow plants on them and are great places to place decorative rocks that you can see through the water. Spend some time drawing out what you want and thinking about how much water you want over the features in the pond before you start to dig.
6. Frog wild
Frogs and other creatures will find the pond and will love to hang out in and about rocks you put in it. You need to plan for this and avoid making the pond too small. The pond may look big when you dig it, but as you fill it with stones and rocks, all of a sudden there will be little room for water.
7. Rolls rock
The best liner for a small garden pond is black commercial rubber roofing material. It comes in giant rolls, and you can often get a nice leftover scrap at a decent price. Call several commercial roofers and see who can supply what you need. Buy the biggest scrap you can find. You want to avoid seaming the rubber at all costs.
8. Curb enthusiasm
Make a dirt curb that's at least 5 inches high around the pond. Lap the rubber roofing over this curb and extend the rubber at least a foot into the yard around. Place rocks on the top of the curb to hide the rubber and to hold it in place. This curb stops surface water from flooding the pond during heavy rain.
9. Fall for it
The most challenging aspect of the pond is creating the waterfall. You can make a stone cliff of sorts to create the elevation needed for the fall. Try using a 1-inch (inner diameter) black rubber hose to connect the submersible pump that's hidden by rocks in the pond to the outlet at the top of the waterfall.
10. Hide and soak
Use another piece of rubber roofing material to help you construct the waterfall. This piece drapes into the pond and you hide it with rocks. The purpose is to catch any water that runs down the rocks. If you don't do this, water from the pond can soak into the surrounding soil and effectively drain your pond.
11. Pump it up
The electric power that feeds the pump must be protected by a ground fault circuit interrupter, or GFCI, outlet to prevent shocks. If you don't know how to install one of these outlets correctly and safely, hire a professional electrician to do it.