You can make your own rain barrel or purchase one. In any case there are some features to consider. Make sure the top is covered to keep out debris and mosquitoes. Some come equipped with a solid lid with an opening just big enough to accommodate the downspout. Others use a screen to keep out debris while letting in the rain.
The spigot should be low on the barrel so water does not stagnate at the bottom. Use the spigot to fill watering cans or attach a hose for watering. An overflow outlet is necessary for periods of heavy rain and for interlocking several barrels.
A downspout diverter is another way to manage rain barrel overflows.
The choices are many making it easy for you to conserve water and grow a beautiful landscape.
A bit more information:Start your conversion to rain barrels one downspout at a time. You can capture as much as 650 gallons of water from 1000 square feet of roof in a one inch rainfall. This can be a lot to manage when first adjusting to this change of habit. Taking little steps allows you to successfully match the use of rain barrels and other rain harvesting techniques to your gardening style and schedule.
We had a nursery plant 15 arborvitae trees in May 2003. We mulched them and then watered them about once a month or less or more depending on rainfall. A number of the branches turned a rusty color. Eventually 6 of the trees died. The nursery replaced them this past spring and the same thing has happened.