Seeds are obtained if a pistil on a plant is fertilized with pollen from the anther of a plant, whether it be the same plant or a different one. The ovary of the plant swells and when it dries it produces a seed pod with hundreds of seeds. These can be planted and raised to blooming size and the grower will find numerous different plants.
Suckers can be removed from the main plant and potted up to obtain plants of the same type. Probably the most widely used form of propagation is a leaf cutting. Intermediate mature leaves produce the best plantlets. Rooting powder is not necessary and in fact inhibits the production on new plantlets by only producing many roots, plantlets will take longer to appear.
The first step in propagating a leaf is to cut the end of the petiole (stem) diagonally with a sharp knife or razor. Leave about 1" to 1 1/2 " of the petiole. Since plantlets develop from the cut end, you will find you get more from a diagonal cut and if the petiole is too long it will take longer for the plantlets to appear. If the petiole is broken, you can cut a "V" shape to create a new petiole.
Use a small plastic pot or bathroom cup. Write the name of the plant on the pot with a marker or on a plastic plant stake. Fill the pot with dampened mix. I use my 1-1-1 soil mix which is extremely light. Others use a mix of 50/50 coarse perlite and coarse vermiculite. Make a hole in the mix with a pencil or similar tool. Place the petiole in the hole up to the base of the leaf. Firm the mix around the stem and place the entire pot inside a clear plastic bag. Some leaves are too large so it is permissible to cut part of the top of the leaf off. This also stops the growth of the leaf and permits all the energy to go into growing plantlets. Inflate and seal the bag and put it into a bright but not sunny location. Check it weekly to see it has not dried out. In four to six weeks you should see small plantlets coming up from the mix.
When the plantlets get to be about 2 - 3 inches in height, open the plastic bag and let the small plantlets begin to harden off. Plantlets may then be removed and potted up separately.
As I said there are many ways of propagating. Many growers years ago used the water method of starting plants from leaves. A glass was filled with water and covered with a piece of foil or waxed paper. A slit was made in the top and the leaf inserted into the water. This was put into a bright area and eventually roots and small plantlets developed. From here growers would transfer them into soil mix. It is now thought that those water roots die off and soil roots have to develop before the plant can grow, which starts the rooting process from scratch.