Spray bottle with filtered water
Any size container (preferably glass to be able to see your substrate)
House plants ( or native plants, but they can be picky)
You don't have to use activated charcoal unless you have a sealed container for your Terrarium. If you do, then it's a must. I am using it in this instructable for demonstration purposes. The charcoal helps keep the water clear of buildup of microorganisms that might grow in your substrate, such as algae and keeps the air clean for your plant to breathe. Besides, who wants a smelly plant in their house?
The type of plants you use can be almost anything, but it ALL depends on the container. If you have a plant that will outgrow your container size, or the environment is not one it can grow in (given time, a cactus will rot in a moist closed container), then you'll be kicking yourself later. Do research on what your using beforehand and your plants will be all the healthier for it.
In this instructable I used African Violet, Spike Moss, and dwarf Sword Fern.
For a list of suitable Terrarium plants, follow this link: www.thegardenhelper.com/terrarium~plants.html