The Barrel

• To make the barrel itself, find an old unused barrel or plastic trash can. Clean it out thoroughly and make sure there are no leaks in it anywhere. If there are, patch them fully, otherwise it won't work as a barrel to hold rain over a long period of time. Ensure the barrel also has a top to affix over it, so that when it is not raining, the water is protected and can stay fresh, and insects, like mosquitoes, won't be prompted to lay their eggs in it.
  
  

Overflow

• It is essential to install an overflow at the top of the rain barrel so that if the barrel becomes full, it won't literally overflow and cause erosion around it. An overflow will attach to the side of your rain barrel and divert water that gets to a certain point near the top to a downspout with a valve that can flow into the line for the gardening hose. This is also handy when you use the rain barrel water for your yard or garden.
  
  

Hose Adaptor and Spigot

• By adding a hose adaptor and spigot, you will have easy access to the water inside your rain barrel. Drill a three-quarter-inch hole in the top and bottom of the barrel. Attach a spigot to the bottom by wrapping it four to five times in Teflon tape and coating it in all-purpose adhesive caulk so that it doesn't leak. Insert it into the bottom of the barrel.
  
  Next, twist the threaded side of the hose adaptor into the hole at the top. You'll want to make sure the adaptor fits into your hose before doing this; then attach your hose to the adaptor and wait for it to rain.