I used and combined several ideas I saw on Instructables.com as well as other websites. I acquired a number of 5 gallon "pickle" buckets with the lids to use for this project. Being lazy, I combined the upside down planters I created with a drip irrigation system with a timer that COULD be the subject of another Instructable, except there are plenty of commercial websites that explain adequately how to create such a drip irrigation system. I combined that drip irrigation system with a "funnel" made of a one liter pop (soda) bottle with the bottom cut out "funnel style" to collect water from the drip irrigation system and channel it into each 5 gallon bucket planter.
Step 1: Preparing the 5 Gallon Bucket
Use a 2" hole saw, drill a hole centered on the BOTTOM of the bucket.
Now take a double layer of paper towel and place it FLAT inside the bucket, covering the 2" hole you just drilled.
Fill the bucket all the way to the top with your planting soil.
Snap the lid on the bucket tightly.
Now invert the bucket with the dirt inside, the lid snapped on tight, so that the bottom with the 2" hole you drilled in the bottom is facing up.
Using a sharp knife, cut an "X" into the paper towel so that you can access the dirt underneath.
I used tomato seedlings purchased from the hardware store, and planted them into the dirt in the bucket, pushing the seedling through the hole in the bottom of the bucket and paper towel "liner", then arranged the paper towel back around the tomato seedling. Leave the planter on its lid for the next 10-14 days, giving the tomato seedling a chance to grow and develop so that its roots expand in the planter/bucket and "lock" the plant into place so that it can be inverted.
Step 2: Inverting and Hanging Your Tomato Planter/bucket
REMEMBER, tomato plants like plenty of sunshine - pick your location accordingly.
Make sure whatever structure you choose to hang your planter/bucket is strong - 5 pounds of damp soil and a fully developed tomato plant can be a bit heavy. Additionally consider the wind load and other environmental factors.
Lift the planter/bucket into place, invert/turn it over, and hang it by the bucket's wire handle.
Step 3: Watering Your Tomatoes
I created a "funnel" by cutting the bottom out of a one liter (16-17 oz.) plastic pop (soda) bottle. I inserted the neck of this funnel (the top of the one liter bottle with the lid removed) into a 1" hole I drilled into the center of the bucket lid that is now the top of the planter/bucket. The fit is tight, but that is good - it will keep your water "funnel" from blowing out of the bucket in the wind. Force the threads of the one liter bottle neck through the 1" hole you drilled in the planter/bucket lid so that water is channeled into the dirt inside your planter/bucket.
Being a labor saving (lazy) person, I used a drip irrigation system with a timer I installed around the perimeter of my porch to water my tomato planter/buckets each morning. I simply fit the drip irrigation lines into the one liter funnels fit into each planter/bucket. All I had to do was periodically prune the tomato plants and regularly pick my tomatoes.