May I ask, how best to search for an ancestor from Germany or Prussia before 1800's.
Olive Tree Answer: Dear Linda: The best place to start learning about German genealogy is at genealogy.net
There are many how-tos, valuable maps, gazetteers, explanations of the political boundaries at different historical periods.
A warning, though. One which holds true for doing research in any country other than the one you are in: Get everything you can in your own country first. You will need precise dates and locations. Do not expect to be able to find country-wide vital record indices, do not expect helpful resources akin to the SSDI, and do not expect records (or websites) to be in English.