If you don't want to disturb the whole plant, knock the soil ball out of the
pot and take a few of the long black roots off which will likely be coiling
around the bottom of the pot, making sure they are live roots. Cut them into
1 inch lengths and place them vertically in a sand/peat mix with the tips
just at the soil line. Treat as per other plant. This is best done during the
growing season and will often yield more plants than you need.
If there are several plants in one pot you can also divide the entire
container which will give mature plants. Again, you may end up with several
pot fulls.
Cliff