This is a small terrarium I made for a friend last fall. I had a glass bowl at the house, and thought it needed to be put to good use. I purchased a zebra Haworthia succulent, and found some old rocks, dirt, and sand at my house. That's all you need! For all my succulent garden and terrarium posts, click here.
First I put some rocks at the bottom of the bowl to allow drainage. You don't want a succulent to ever sit in water, so the rocks in theory help keep the plant sitting above any water that pools at the bottom after watering.
Next I put in some sand, then dirt, then the succulent, then some more dirt. The idea is to get loose, sandy soil. You can make this all simpler by just using succulent/cactus soil instead of mixing sand and dirt.
Lastly I added finishing touches: polished river pebbles and some seashells. Done! The plant has been doing quite well for half a year so far. You don't need to water these very often, which makes them easy plants to have around the house.