Using our molds and making things with plaster and cement is very easy and fun. Before you start there are some things you will need:

Plaster, Cement, or Mortar mix
Mixing Bucket
Tool to Mix With
Water
Lubricant i.e, Motor oil, WD40 or Cooking Spray
 
 
Prepare Mold: I always lubricate the mold before pouring plaster or cement in. It will make your casting come out easily, plus it will make the mold last longer. I always use 5W-30 motor oil, In my opinion, I  don't believe the commercial mold release being sold is any better.

As far as whether you use plaster, cement or mortar that depends on what you are making, and your personal preference. Portland cement has a very smooth light colored stone, yet it will not be as strong as the mortar which is cement with sand. Concrete mix can also be used, which is cement, sand and aggregate(small pebbles)...It is not as smooth as mortar or cement, yet it makes a stronger item.Quickcrete and other mixes can also work just fine. I like working with plaster so much because it is smooth and is dry in only 30-45 min...cement will take about 24 hours. Sometimes people shy away from plaster because it is fragile, but if you paint and seal it...it will be much more sturdy and will have a porcelain type of finish.
 
 
Once you gather the items you will need and decide what type of medium you will be using with your mold...You will want to make sure the mold is clean and give it a very light coating of motor oil and set it aside.

Mix the plaster or cement in the mixing bucket with water. I usually put the plaster/cement in first, and then just start adding water and mixing. What you want is to have a pancake batter type of consistency, then you will be ready to pour it into the mold.

Filling Mold: Start by pouring only half of the mixture into the mold. Gently shake and tap the bottom and sides of the mold to eliminate all bubbles. Then pour the remaining mixture. Shake and tap again until the surface is flat and even. Keep the mold in a dry area to cure 45 minutes for plaster or 24 hours for cement on a level surface.

To Unmold: Gently turn the mold upside down onto a soft surface, like grass for example, and pull sides away very gently from mold and tap lightly on the back. Do not walk on your stones for 24-48 hours to make sure the mortar/cement is set all the way through.