I use a lot of recycled materials in my small garden including 1.5L soft-drink bottles, 1L yogurt containers, 3L ice-cream containers and 20L buckets for raising seedlings and for growing out various crops. The following steps outline how to construct a very effective self-watering container from a 20L bucket and a product I have recently discovered.
Step 1: Of course is to collect and thoroughly clean a bucket, in this case I have a couple of 20L buckets sourced from a bakery.
Step 2: Drainage holes need to be cut into the bottom of the bucket for instances when the self-watering reservoir overflows. I didn't have a drill so I just used a sharp knife to twist drill a couple of holes into one sufficiently large hole.
Step 3: The holes need to be covered sufficiently to allow water to flow out but to keep your soil in. A thin layer of coarse gravel would be ideal but I've opted to recycle a couple of 'body scrub sponges' that I've uncoiled.
Step 4: I recently discovered this product at my local nursery which for $4.80 saves me a lot of time setting up my own dodgy self-watering insert! Basically it's just a bowl with a flat perferoted lid that can collect water at the bottom of your container, which can be utilised by roots when required.
Step 5: I place a thin layer of soil in the bottom of the bucket to accommodate and stabilise the plant water well and then because I'm growing plants that need supporting I've inserted an old broom handle and stabilised it with some wire also sourced from the bakery.
Step 6: Then as I do with all of my containers I add a few layers of soil with blood and bone, Water-Storage Crystals and a Rechargeable Solid Water bag as outlined here: http://veggie-might-sp8.blogspot.com/2009/08/water-management.html
Knock together a trellis from some cheap fencing and you double the range of vegies you can grow in them.