This can be accomplished in a near infinite amount of ways. Meditation, series of poses (Sun salutations in Yoga, for example), dancing, singing, swaying, candles, etc. A good place to start would be grounding. This form of energy work allows you to both wax and wane with energy and bring you to a level place. You'll feel the swell of gathering energy as well as it's ebb. In order to fo this there are numerous methods.
Go outside barefoot onto the dirt, close your eyes, and take a deep breath. Be aware of the energy of the Earth beneath you.
(If the first isn't reasonable for some reason) Find a position that's comfortable, personally I sit. Feel roots growing down into the Earth toward its energy and warmth. Draw the energy into you on an inhale and push energy out on an exhale.
Casting is the release of the energy. It's like gathering a bundle of objects and then tossing them on the ground. The raising is the gathering and the casting is throwing them down, an important part that I hope you haven't skipped over, is the imbuement of desire or the imprinting of intent on the gathered energy.