- Find a good sized bottle
- Use it upright or turn it on its side
- Layer damp sand and small pebbles on the floor of the bottle. Consider a layer of activated charcoal to absorb any smells and a layer of moss to keep the soil from settling. Add your soil. Choose seeds from small plants with similar requirements that can stand a good deal of humidity.
- Place your mini-greenhouse in medium sun and tend it carefully.
For more details, see WikiHow. (image via Medoria's Flickr Page)