Whether it's houseplants or annuals, many folks take a snip of their favorites and place them in water to form new roots. But Bobby isn't a fan of this method because the plants roots can be spindly and weak.
Instead, Bobby suggests cutting a small section of plan just a bove a leaf node. Pinch off all but the last few leaves of that section. Dip the cut end in water then rooting hormone if you have any, although this step isn't absolutely necessary. Finally plant the tiny plant in good quality potting soil.
Make sure to keep it moist in the coming days. Losely enclosing it in a plastic bag can help the new plant thrive by increasing humidity for it.
Give it a gentle tug after a couple weeks. If it resists that means a good root system has started to develop and you can repot if you wish.
Keep in or near a bright window and water throughout the winter when the top 1" of soil is dry.
This method works especially well for coleus, impatiens, begonias and geraniums.
Good luck!