Fill a pot that has drainage holes with a sterile rooting mix that contains vermiculite, coarse sand or perlite. Add water to dampen the mix, but don't allow the pot to stand in water. Use a stick, pencil or straw to make 1-inch-deep holes spaced 1 or 2 inches apart.
Select strong stems on the geranium to use as cuttings. Cut 3- to 4-inch sections from the tips of several stems. Cut off any leaves on bottom section of each cutting.
Put a little bit of rooting hormone in a small plastic bag or other small container. Dip the lower part of the geranium cutting into the hormone. Place the cuttings in the holes.
Place a large plastic bag over the pot. Find a warm location with indirect light to keep the cuttings. Check the cuttings at least once weekly and water as needed to ensure the growing media remains moist.
Check for roots on the geranium cuttings in six to eight weeks. Carefully pull on a cutting to see if there is any kind of resistance. If not, wait several more weeks and then check for roots again.
Repot rooting geranium cuttings into separate 4-inch pots filled with potting soil. Plant them at the same depth and slowly over several days accustom the cuttings to direct sunlight.
Water the plants as needed to retain moist, but not soggy soil. Grow the geranium plants larger and stronger before transplanting them.