There are a lot of bird feeders on the market, from inexpensive to expensive and from plastic to glass and metal. Which one is right for you?
We recommend starting out inexpensive. Try to figure out which birds you would like to attract. Do you want colorful birds like goldfinch and Blue Jays? Or would you rather songbirds? Maybe woodpeckers or hummingbirds? Unless you would like to attract hummingbirds or orioles, you can get a generic type of bird feeder, like a tray feeder or a hopper bird feeder and both will support a variety of bird seed. (Hummingbird and Orioles eat nectar, so there are specialized nectar feeders for both of them.) You can feed nearly any mix from a platform or tray bird feeder and there is plenty of room for perching birds. The problem you will have with this type of bird feeder is squirrels. If you live in the US, and you have mature trees, you will probably have issues with squirrels. There are ways around this, with squirrel proof feeders and hot pepper flavor on your seed.
Once you find the bird(s) you'd like to attract, you can start looking for a more "specific" bird feeder. For example, Goldfinch will eat sunflower seeds from a tray or hopper type bird feeder, however, they LOVE Nyjer Thisle seed, and you can get rid of other birds you don't want to see, by putting up a finch feeder, which feeds only thistle seed and has no perches. Many birds cannot "cling" to a bird feeder without a perch...but finch are part of the group we birders call "clingers". Other clingers include titmice, nuthatches and woodpeckers.
To attract woodpeckers, try offering nuts or chunks of suet in your tray feeder, if they come, you can add a suet cage feeder, or even be more specific get an upside down suet feeder, which only allows clinging birds, like woodpecker. Starlings and sparrows generally will not be able to cling to the bottom of an upside down suet feeder, but the woodpeckers will get used to it.
Cardinals are easy to attract in Wisconsin, just put some black oiled sunflower seed into your tray feeder and the cardinals will come. To keep the sparrows out, switch over to striped sunflower seed or a mixture of sunflower and safflower seed. Sparrow and other birds are not able to crack into the heart of a striped sunflower seed, but a cardinal's beak will crack it!
Adding a water source to your backyard will also help the variety and quantity of birds you attract to your backyard and running water or moving water is even better. Mosquitoes will not lay larvae in moving water and birds can hear the sound of water and will come in to it, they can't hear standing water.
Another problem you will quickly encounter is birds flying into your windows. There are several options to help reduce ths. Birds can be territorial, and when they see their reflection, they think their territory is being infringed upon. So, the way to stop them from flying into the window, is either to not let them see their shadow or to limit the impact on the window. This can be done by putting your feeders near windows with screens, or putting bird netting taunt around the window, so the netting baffles the birds' flight into the window. Another option is installing exterior blinds and keep them closed, unless you are enjoying the sunlight or view. You can also purchase bird window clings, which lets the bird see the window, so they won't fly into it.