This is my "recipe" for a Container Garden using Rubbermaid containers. It is a cheap and effective way to garden, and is very easy to get together.
Second, prepare your containers. Drill 3/4" holes in the bottom and around the bottom sides of the container. You can use the lid, placed up-side-down, as a good drainage catcher, but make sure you have something to lift the container up off the lid so that air can get underneath, and so that the excess water will actually drain. I used deck banisters cut in half. I used a few pieces per container, placed them on top of the up-side-down lid, and then placed the containers on top of that. I was also mindful of where the drilled holes were in relation to the banisters and tried to make sure that none of the holes were blocked.
After I finished planting, I added a layer of mulch on top of the soil. This helps retain water and also protects the soil... and it also looks good. :)
And there you have a container garden.
Remember to water well and watch them closely.
Oh, and talk to your plants - it makes them happy!
Edited to add:
I would recommend this form of gardening for your non-food-bearing plants.
The discussion regarding the release of toxins from the plastic containers into the soil and thereby the food is an interesting one that would require more research. And if you have insight, please feel free to share in the comments!
But all in all, still a great option for a garden!