On my Genealogy Roots Blog I now have three articles that may be
helpful for finding German genealogy records for Americans who have
German ancestors...

Here's a useful starting place if you don't know the name of the
village or town your German ancestor came from:

Tips for Finding Your German Immigrant Ancestor's Hometown in Germany

Once you know the name of the village in Germany then you might find
this article helpful:

Tips for Finding German Genealogy Records for Your German-American Ancestor

And here's an example of how some German church records were obtained
where the LDS Family History Library didn't have microfilm for that
particular parish:

How I Found Some Genealogy Records for My German Ancestors

For more tips for doing German genealogy research see:
German Roots - Genealogy Information for Americans of German Descent