General Feed
Only a handful of foods are attractive to most wild seed-eaters, and these foods are naturally unattractive to birds who don't eat seeds. However, for a general purpose bird feeder, they make good choices. These foods are black oil sunflower, cracked corn, hulled sunflower, white proso millet, Nyjer and whole peanuts.
Hummingbirds
Attracting hummingbirds requires going beyond seed. The best and simplest thing to do is to mix 1/4 cup sugar per cup of water, and put that in a specialized feeder made for hummingbirds. The sugar water in the feeder should be dumped and replaced every day or two, lest it become a breeding ground for bacteria. For the same reason you should use table sugar and not honey, molasses or some other kind of sweet stuff. When diluted with water, those substances are very prone to infestations of bacteria and/or fungus.
Meaty Stuff
Some birds have a taste for meaty protein, whether from hunting insects, other birds, small mammals and reptiles or feeding on carrion. Suet, for example, is a good choice for bringing in chickadees, jays, woodpeckers, nuthatches and starlings. Sometimes it also attracts creepers, kinglets, cardinals, wrens and warblers. Bacon drippings and mealworms are other choices for these kinds of birds.
Fruit
Putting fruit in your bird feeder is a good way to attract bluebirds,catbirds, robins, thrushes, waxwings, mockingbirds and tanagers. Use fruit such as fresh or frozen berries, apple and melon chunks and individual grapes. Raisins, cranberries and dried currants are also good ideas, but these need to be softened with a little soaking in water before being left out. Halves of oranges are of particular interest to orioles in the midst of their spring migration.