To start off, your research strategy should be focused on finding the last residence or at least the area in Germany your family came from. Then, you can identify local or regional resources. For this purpose, passenger manifests, including lists of arrivals at U.S. ports, or departures from Germany often provide very helpful information. Those include established large databases, provided by commercial firms for fees, or those offered for free by societies or other institutions.
The next steps lead you to state archives, church archives, and civil registration offices of communities, towns or districts. Also, local databases, including name-lists, family and local history publications are helpful. You will notice that archives in Germany – be it church or state archives, Germany-based web sites from genealogical societies, church offices or groups of volunteers - do not always provide English-language navigation or explanation. Therefore it is recommended to contact them directly. Be prepared that many of the institutions or organizations may not have the resources to carry out research, or that they need time to work on your request. Nominal fees may apply.