If you find a baby bird that is too young to fly, put it back in the nest. The mother will appreciate the help.
However, if you find a baby bird that is old enough to fly, but isn't, chances are it is learning. If you look, you will see the mother nearby. Leave these older birds alone and let them learn to fly undisturbed.
If you're not sure call for help before you do anything. For a list of licensed rehabilitators click HERE. Or to search for a local wildlife rehabilitation group: http://www.wildliferehabber.org/ and the Michigan Department of Natural Resources: http://www.michigandnr.com/dlr/