The first thing the birds need is food. A simple bird feeder with mixed seed can provide your birds with food, or you can go for something more complex, to attract more species of birds.
Thistle seed will attract many species of birds, such as some finches, that other wise would not come. Likewise, you may want to put out suet, or other “special” foods to attract more birds. Of course, during the summer, put out a hummingbird and/or an oriole feeder.
The second very important thing birds need is shelter. Birds have many predators out to catch them – everything from hawks to cats. Some people will go so far as to build brush piles in their yards to shelter birds, but that is rather unsightly, to say the least. An easier solution is to plant a flower bed filled with some evergreen bushes, ground cover, etc. It will look great, and provide a haven for birds.
Another thing that you can offer birds is a bath. You can provide them with a typical water bird bath, or you can provide them with a dust bath. A dust bath can be as simple as a patch of sand underneath the bird feeder. Nothing fancy is required!
Last, but not least, you'll probably want to provide your birds with nesting houses – a safe, dry place for the to raise their families! Of course, be sure that you choose appropriate houses for the species of birds that you have nesting in your yard. If you're fortunate, you might get to watch a pair of birds raise their young – few things are more exciting to watch.
In summary, give birds what they need and want, and they will come to your yard – and you can enjoy their colorful beauty.