Lay out newspaper to cover the area in which you will be working. This is a craft that is best suited for outdoors, the garage or the basement, but if the only space you have to use is your kitchen table, you will do fine as long as you take the time to prevent any damage from stray concrete.
Select a mold for your stepping stone. Molds can be purchased from craft or home improvement stores, or you can use something in your house, like a cardboard box or a cake pan. If you use a porous material, such as cardboard, line it with plastic wrap so that the moisture does not leave the concrete and absorb into the box.
Put on plastic gloves and mix your concrete, being careful to follow your package directions. If you are only making one mold, do not make extra concrete. If you wish to use all of your concrete at once, make several stones.
Pour the concrete into your mold, or molds. Make the depth of the concrete at least 2 inches thick, as this will make a sturdier stepping stone. Do not make it more than 3 inches thick, as it will take too long to set.
Allow the mix to set for at least 30 minutes before you begin decorating. When it starts to set, you can get creative. Decorate the top of the concrete with marbles or stones, use broken glass to form a mosaic design or have children put their hand prints or foot prints in the stones and write the date with your finger or a craft stick.
Allow the concrete stone to set for another 24 hours before removing it from the mold. After it is out of the mold, set it outdoors to air dry for 10 to 12 hours before placing it in its final location.