Home improvement stores, catalogs and online vendors offer them in metal and plastic, or, any large container can be recycled into one.
The simplest method is the old fashioned one of putting a barrel under your rain gutter downspouts. Other easy methods are to use a rain-chain to divert the water or to connect a water barrel to a downspout by removing the bottom portion of the downspout.
Look at the options available in home improvement and garden centers to see what is in your price range and is realistic for you to set up.
Choosing the right rain barrel size will depend on what you intend to do with the water, how big a footprint your landscaping can hide and how much rain you hope to capture.
To raise seedlings, an average sized rain barrel is big enough; for a large garden install a 1,500 gallon one. (A 1,000 square-foot roof gets 625 gallons of water from a 1-inch rainfall.)
There are many attractive rain barrels on the market but most of them would never be considered a lawn ornament. Look around the landscape and choose a place where it can be hidden from view with shrubs or a decorative fence.
Rain barrels should be kept covered to keep leaves and insects out. They also benefit from a filter to prevent silt – something as simple as a funnel with mesh at the bottom and covered with gravel.
If you prefer to use a few rain barrels connected together with PVC pipe or a length of hose, a pump will be needed to move the water from all the containers.
Some rain barrels, such as the Fiskars models, come with a downpipe diverter kit that fits into the downspout, or one can be purchased from a hardware store or easily made.
Your installed rain barrel should be placed on a secure surface, such as concrete pavers. Plan well since a barrel filled with rainwater will weigh a substantial amount since water weighs 8 pounds per gallon.
Another planning consideration is to put the rain barrel high enough on a platform of some kind so you can get a watering can under the spigot and have enough gravity to make the water flow.