Lay out string where you want the concrete pathway to be. Run the string along both sides and secure with stakes.
Dig up the sod 6 inches deep between the strings using a spade.
Add one layer of compactible gravel, and compact with a hand tamper.
Set up 2-by-4inch lengths of lumber along the edges of the gravel. Secure the lengths with stakes, hammered in on the outside at each joint, for a better seal when pouring the concrete.
Insert lengths of #3 steel rebar in between the lengths of lumber. This will be added reinforcement for the concrete pathway, which will run parallel to the sides of the pathway. For example, if you have a pathway that is 2 feet wide, place the rebar 8 inches in from each side.
Clamp each rebar in place with bolsters.
Mix your concrete in a rented mixer, using the manufacturer's recommendations. To mix, combine the gravel and cement with water and sand until it's a thick consistency, such as that of oatmeal.
Pour the concrete on top of the rebar and in between the 2-by-4-inch lengths of lumber. Level the top with a screed board.
Tap the sides of the lumber and the top of the concrete with a hammer. This removes pockets and helps strengthen the concrete. Re-level when you're finished.
Use a wood float to get a smooth surface. Then, push a stiff broom over the surface to create texture. This makes the pathway more slip-resistant.
Wait for the concrete to cure. Then, remove the lengths of lumber. Fill in that space with dirt.