Determine where you will take one or more cuttings from your jade tree to clone. Note that the plant will die back to the nearest node---the point of origin for a pair of leaves. Consider choosing large internal clusters that are crowding the plant's canopy, in order to give the parent jade tree a better shape.
With scissors, cut leaf pairs back to the node or remove entire stems back to the main branch. Place your cuttings on a clean towel and leave them on a high shelf overnight.
Check your cuttings in the morning to see if the stems have crusted over. If not, leave them exposed to the air until a thin skin forms over the stem. This could take anywhere from 24 hours to one week.
Once the stem has crusted over, stick the cutting in a pot 3/4 full of potting soil and loosely fill the remaining space with soil.
Water the plant thoroughly. As the water compacts the soil, you may need to add more and repeat the watering.
Place your new jade plant in a sunny spot. Though it will take some time for your plant to grow substantially, you will have a clone of your jade tree to decorate your house or give as a gift.