In addition to bird feeders and bird houses, bird baths are a another feature to attract birds. Available water ifor drinking is essential to most birds (some get all their water from their food) but a bird bath is more than that, hence the "bath."

A bird doesn't take a bath like we do, immersing ourselves in a big tub of water. Rather, they shower. The dip their head, flick their wings, and water droplets cascade over the bird. After getting enough water in and over the feathers, the bird will preen itself by pulling its feathers through its beak. This removes dust and dirt and feather mites. The bird rearranges its feathers and spreads waterproofing oil on them, the oil coming from the preen or uropygial gland at the base of the tail.

The bird bath can be most any shape, but it should be shallow as most birds only want to wade in it a bit, not swim. It should have rough sides so the birds do not slide into the water. Or you can add gravel or paint it with friction paint. Place it anywhere but make sure that there is cover nearby so that the birds feel safe.
If you can arrange it so that water drips into the bath slowly, this will make the bird bath even more attractive to songbirds. And a submersible heater in winter, if you are in a place that freezes, would be nice.

Clean your bird bath frequently with a dilute solution of Chlorox and rinse well. Any remedial bleach will disappear within a day so it's no danger to birds. If you want to paint your bird bath, use a paint made for boats, it will protect the bird bath and won't leach into the water after it dries.

More Information about bird baths at All About Birds and Fountainful.