Introduction to Ships Passenger List 
In 1876 I. Daniel Rupp's milestone book "A Collection of Upwards of Thirty Thousand Names of German, Swiss, Dutch, French and Other Immigrants in Pennsylvania from 1727 to 1776" was first published. Almost twenty-five thousand of those thirty thousand names were from ship passenger lists, most of which represented ships that departed Rotterdam, Holland and were bound ultimately for Philadelphia. Each voyage was recorded separately and so searching required looking separately on approximately 320 different lists. For this presentation everything was combined into a single master list and then alphabetized so that names could be searched alphabetically.
There will still be problems in identifying many of the surnames. Just a casual look at the list makes it obvious that there was some confustion in translating the German names into English text. In Rupp's original text he has flagged the names that were written by the immigrants themselves. Rupp's original text is now online and if a name is found that resembles a certain surname, that text could be checked by going to http://www.archive.org/stream/collectionofupwa00ruppuoft#page/n7/mode/2up to see if the name was self inscribed.
Mostly only males age 16 and over were listed. However, on some of the lists a separate section for males under age 16 was included. Many of these ship's lists have been published separately and can be found online, and many of them have names not included in Rupp's book and this would include names that have been found from other sources.
When searching for specific surnames it is a good idea to imagine what the name would have sounded like phoenetically and then search for alternate spellings. For instance at the beginning of names G and K will sound very much alike to an English language listener. The same could be said for B and P. My own Bickel ancestors were often recorded as Pickel. Whether or not any bilingual persons were involved in making these lists is not known. Often Rupp, the original author, spelled the surname differently even when it was obvious that they were members of the same family. I think this may have been done to illustrate that there were probably many errors of spelling.
The five thousand or so names from the book that were not on the passenger lists represented other early German settlers in Pennsylvania, New York, Virginia and the Carolinas. Since ship passenger lists were not required before 1727, this is a good source to look for those who came before 1727.