Hi there!
Fractal (one of our savvier members) answered this question pretty fully yesterday:

"They are relatively simple to propagate. Simply cut below a rosette of leaves to the length of stem that you want it (between 4-6ins is ideal). Leave to dry the cut end for a few days and pot up into something like John Innes seed compost with maybe a little extra grit added for free drainage. Don't put into too large a pot initially as the soil needs to dry off quickly between watering so 3in pot is ideal. This time next year or maybe June at the earliest it can be potted on into a slightly larger pot.

The cut end of the parent plant will produce two or three new rosettes from the sides just below the cut and these will grow on into new branches."