Mix potting soil and coarse sand or perlite half-and half and fill your containers. Clean your clippers with a solution of 1 part chlorine bleach to 10 parts water.
Choose healthy plants with no pests or diseases for your cutting stock. Clip off branch tips 3 to 5 inches long and remove all but the top three leaves.
Dip the cut ends into rooting hormone and tap off the excess. Poke a hole into the potting mix with your finger. Stick the cutting into the hole and firm the soil around it. Stick four cuttings per 4-inch pot or three cuttings per 3-inch pot. Cover the container with a plastic bag and place in a warm spot with indirect, bright light.
Keep the cuttings moist, but not wet. Check for rooting by tugging gently on the cuttings after 4 weeks. If they resist, remove them and place them into their own pots in a well-draining potting mix.
Fertilize your pelargonium cuttings once new growth begins. Pinch the tip of the cutting out once the plant is established in its new pot, to encourage branching. Gradually move the rooted cuttings into brighter light until they are acclimated to full sun.