One of the most common materials use for making a ramp is plywood. Its availability, durability and easy sizing options make plywood the ideal ramp material. You can visit your local lumberyard or use the Internet to find your desired size and price for the plywood sheets needed for your ramp.
Depending on the size of the ramp, its desired strength and its angle in relation to the ground, blocks of various materials can be used. Consider concrete blocks for steeper ramps, and bricks or small wooden blocks for lower ramps. Depending on the type of ramp you're building, blocks may only be needed at one end of the ramp or not at all.
To finish the job, purchase a bucket of your favorite exterior paint and give the plywood a thorough coating; or lay down carpet and tack it securely on the underside of the ramp. Another option offered by Arkansas.gov is to use a rubber mat glued to the ramp to provide a non-slip surface. This is a good solution for indoor or outdoor use.