Many types of bird houses and nesting materials are available. There are three basic types of houses:

Bluebird Houses:
Shape and size are very important. The location of this entrance hole and the size of this hole are critical.  There should be no perch. Most often bluebird houses are put up on posts or trees in the open buy close to the cover of shrubs and trees. Put up two or more.

Nest Boxes (Houses):
These houses attract various types of birds. Entry holes need to be large enough to accommodate larger birds. The box can be placed at almost any location.

Wren Houses:
These are small nest houses that are suited for wrens and other small birds. There should be no perch. The house should be easy to open for cleaning. Hang from a tree branch or pole, and it is best to put up two or more.

Note:
Put all houses in areas not accessible to cats and other predators.

   (source: wilddelight.com)