Many of my recent clients are trying to find their ancestors place of origin. I know what that feeling is like since for many years I thought about where did my paternal surname originates from? There were family stories I heard that maybe they came from Westphalia, Alsace or Lorraine regions of Germany. I never questioned that family information until I began to activate my place of origin search about 10 years ago.
Before beginning any search across the Atlantic to the Old Country, I had done years of research on my known Ancestors to the point where I knew their first location in the U.S. My information had sources, and correlated with other collected information about my family, dates of key vital records (birth, marriage and death); much of this done before Ancestry.com became popular.
I learned that though it may turn out in the distant future that the Rettammel family much earlier originated in Western part of Germany, my research had led to northern Germany and former Poland at the time. So Prussia and Pomerania is where I found my great-great grandparents coming to America in 1865.
Prior to approximate year of 1772 most of this was in the Kingdom of Poland but even further back this, area close to the Baltic Sea, was settled and called Pomerania with parts controlled by Sweden.
So one item to remember is that the place of origin may not be what you were told or expected from family lore. Just keep in mind that German heritage does not follow the standard 20th century framework.
So in researching for my clients, I try to inform them that it takes clear confirmation of sources here in the United States before jumping the Atlantic to present Germany.
I also know my contacts in Germany appreciate and can be more helpful when the data collected has a good confidence level.