Terrarium Basics;
Michele Klink, Wilton Garden Club

Open – best for plants like succulents, tillandsia, sansevieria and cacti
Closed – best for plants like  ferns, begonias, African violets

How to:
Choose a clean glass container or jar – with or without a lid (see above)
Create a BASE LAYER with activated charcoal which helps control rot and absorbs odors.
Next add small pea gravel, pebbles or aquarium stones for drainage.  If using a slanted container, add stones and other materials with more height towards the back to give depth.
Next add a layer of sheet MOSS which provides additional drainage and separates soil from stones so it does not leak through.
Add soil in a MOUND in the center.  Then start adding PLANT material.  Taller plants in either the center or back of the container depending on whether your container is flat (center) or slanted (back).
Use rocks, lichen, bark, shells or seed pods to help shore up your plants as well as additional soil as needed.
Finish off the edges with decorative rocks, moss or other materials as you like.
In an open Terrarium that does not require or provide much moisture, you can also use sand (including colored decorative sand) as one of your drainage layers or as a decorative top layer.
Helpful tools:  Spoon, Small paintbrush, tweezers