A bird wants the same sort of things in and around their homes and feeding areas as humans and other animals do. To consider an area safe to feed, birds look for food, water, shelter, and lack of predators. No matter where you live, providing a variety of foliage with plenty of spaces in between for birds to fly in is a standard.
A variety of both evergreen and deciduous trees will provide year round cover and food for birds. Evergreen trees, such as spruce and pine, retain their greenery all year round, offering good cover and shelter for birds. Deciduous trees, such as fruit trees, offer shelter and perch areas in some seasons and food, such as fruit and seed, through others.
In addition to trees, many birds will desire wildflowers and other ground cover. For birds that are more ground-oriented those things will be a necessity. Go to a nearby woods or wooded state park and study the sort of trees and brush growing there, odds are those things would also do well in your yard. Using the plants and trees you find growing natively in your area for your yard landscape will also help the birds to feel more comfortable with their surroundings due to familiarity.
In addition to trees, providing a variety of feed stations and bird feeders throughout your yard will make birds feel safer and more comfortable when they land to feed. The birds will feel that they have more escape routes, and that they do not have to squabble with other birds over food.
The majority of desirable backyard birds consider shallow, slow moving water a comfortable place to bathe or drink. Songbirds are generally not good swimmers, if they can swim at all, so deeper or fast moving water will scare them away. Adding birdbaths to your yard will help attract more birds, especially if they are near a feeding area. If you live in a very cold area, consider purchasing a heated bird bath or a bird bath heater. This will help to maintain an area where birds can get a drink, even in the coldest weather.
Following these basic tips should give you a good start on attracting more birds to your yard, but time and patience is the key.