Determine the type of ramp that you want to make well in advance. Some options to consider include the shape and slope of the ramp. Shape options include a launcher ramp, half pipe, quarter pipe, transfer or bank ramp. Sketch your ramp on graph paper and figure out the full dimensions of the ramp before building. The dimensions of the ramp will help you determine how much concrete that you will need for the project.
Clear the land in the location where you plan to place your ramp. A concrete ramp is very heavy, so you must build a foundation for it as if you were building one for your home. Mark the foundation of your ramp by driving stakes into the soil just outside the corners of the ramp location. Tie string to each stake and stretch the string between the stakes to mark the location of the ramp.
Dig out the foundation for your concrete ramp that extends 6 inches downward. Fill the foundation depression with a 4-inch layer of crushed gravel. Wet the gravel and compact it down with a tamping tool.
Construct your concrete forms out of wood. The concrete forms will create a mold into which you will pour your concrete. Cut the forms out to make the sides, back and slope of the ramp. Join the walls of the form together using wood screws.
Oil the inside of the form with cooking oil. The oil will help the concrete form to pull away from the concrete when the concrete dries. Place the concrete form over the base.
Place 3/8-inch rebar throughout the concrete form and tie it in place. The rebar will help prevent the ramp from cracking and breaking.
Mix high-quality concrete in a cement mixer until it is the consistency of cake batter. You can rent a cement mixer from many building supply stores. Pour the concrete into the form until the level of concrete reaches the top of the form. Tap the sides of the form with a hammer as you pour to dislodge air bubbles.
Dampen the cement with a garden hose. Wrap the entire project in builder's plastic sheeting and allow it to dry and cure. Remove the plastic, spray the cement and re-wrap the plastic daily. Allow the cement to cure and dry for 28 days. This will cause the concrete to dry and harden and will prevent cracking.
Remove the plastic, pull the screws out of the forms and pull the wood off of the surface of the concrete. The ramp should be complete at this point.