Place stakes in the ground, connected by string, to mark the path that you want the French drain to take. Start with the lowest part of your property, where the drainage system will end, and extend the drain to the highest part of the property -- or at least to the area where you are having excess water problems. You can includes branches from the main path that the French drain will take to cover a larger area of your property.
Remove the sod from the path of the French drain, using your spade. Repeat the process to create a 1-foot square in the grass. Dig up the square and place it to the side. Repeat this process for the entire stretch of your French drain, including the branches from the main path of the drain.
Dig a trench that is 24 inches deep from the bottom of your property to the top. Don't worry about digging out the branches just yet; only dig out the main trench. Remove the dirt from the area as you dig, since you will not be reusing it. You can use a wheelbarrow to expedite the dirt removal.
Lightly tamp the bottom of the trench. Starting from the top, lay the 2-by-4 in the trench and place the level on top of it. If the trench is not sloping downward, remove some dirt until it does. The slope does not have to be severe; it can be as little as an inch down for every 20 feet of trench, but it needs to be sloped. Continue this process until you are sure the entire trench is sloped.
Repeat the digging and grading process for any branches from the main trench line.
Place a 2-inch layer of washed gravel at the bottom of the entire trench system.
Wrap your perforated pipe in landscaping fabric so water will be the only thing that can get into the pipe, and lay the pipe into the trench with the perforated side pointing down. You want the perforations pointing down because the water will build up in the bottom of the trench and you want that water to enter the pipe as soon as possible.
Fill the entire trench with gravel up to about 1 inch below the surface. If you plan to place the sod back over the trench to hide the trench from view, do it now. Otherwise, just fill in the remaining inch with gravel.