I made a couple of mini self watering containers for a miniature rose I am trying to save and some peppermint. These work great. You can't over water or underwater your plant (as long as you keep the reservoir bottom full).
I normally make these with 5 gallon plastic buckets, but had these laying around and thought I would make a smaller version. I got the idea off of Youtube.com when I typed in Homemade Self Watering Container.