1. Estimate the Arrival Date
The date of immigration can be found in a number of records including some census records (the U.S. Federal Censuses for 1900-1930 all ask for year of immigration), death records (often recorded "How long in the U.S.?" on death certificates), obituaries, and many other records and home sources. Often a combination of resources can help pin down the elusive dates. Using a combination of birth dates and birth locations, particularly among siblings in the family that immigrated, it is often possible to narrow the arrival date to within a few years. Include your estimated immigration date in your search on Ancestry.com to narrow your results to those that would apply. You can add +/- 1, 2, 5, or 10 years to give yourself a little wiggle room for rough estimates.
2. Gather Identifiers
Sometimes the challenge isn’t so much finding your ancestor’s name in the records, as determining if it really is your ancestor. It’s helpful to compile a mini-profile of your ancestor based on the information you may find in the record.
How old was your ancestor? Census records are also a good source for estimating age at the time of immigration, as well as information from death records, tombstones, correspondence, marriage records, etc.
What did he or she do? Some passenger lists will list occupations. While this information typically isn’t indexed in passenger arrival records, in some cases it can be helpful in "thinning the herd" to focus on the most promising individual(s).
Who might they have traveled with? Family structure can be helpful in locating families who traveled together, although it bears mentioning that it wasn't unusual for the head of the family or some family member to come over first and then send for the family later, once employment and a living space had been secured.
It can also be handy to have a list of other surnames that have appeared with your ancestor. Witnesses and sponsors, neighbors, collateral relatives, and anyone whose name keeps popping up in conjunction with your ancestor, could turn up as travel companions who arrived with your ancestors.
3. Learn Ethnic Names
Our ancestor’s may not have traveled with the Americanized version of their name that we’re familiar with. Look for your ancestor’s given name in his native language. BehindtheName.com is helpful in finding some variants.
For surnames, look for information online and in print publications that can teach you the ins and outs of surnames in the land of your ancestors. For example, the website PolishRoots.org has several articles and helpful resources on Polish surnames.
Search the Internet for other similar sites for your ancestor’s background (e.g., German given names, Hungarian surnames, etc.)
4. Check Multiple Ports
The story of ancestors arriving through Ellis Island is a popular one and although New York was the port of choice for millions of immigrants, many traveled through Baltimore, Boston, Philadelphia, New Orleans, and other U.S. ports (all of which can be searched here). In addition, for many years travel to Canada from Europe was cheaper and you may find that your ancestor took that route to the United States. Border Crossing records from Canada to the U.S. are available for the years 1895-1956, and Canadian Passenger Lists are available for 1865-1935.
5. Don’t Stop Looking
Don’t overlook the possibility that your ancestor may have made more than one trip. Sometimes—particularly in later years when steamships made the trip easier and faster—immigrants made several trips before finally settling in.
Search Passenger Lists on Ancestry.com