Gently twist a leaf off the stem. Make sure it's a clean pull, with nothing left behind. A torn leaf won't grow.
Grab sharp scissors and cut off a piece just above a leaf on the stem. The top of the plant or a new offshoot both work.
Set your leaf or cutting aside for one to three days, so the end can scab over. If it doesn't, it'll soak up too much water and drown.
In a few weeks you'll see tiny roots, then little leaf babies. Keep the roots covered with soil and let the old leaf dry up.