Cast the net wide
The most common mistake made when starting research online is surprisingly counter-intuitive. It is to be too precise. The fact is, the more detail you include when you query a genealogical database, the less likely you are to find anything useful.
Just think. Your John Brennan was born on March 17th 1868 (March 17th being a surprisingly common birthday for the nineteenth-century Irish), married Mary Murphy on September 14th 1890, had children John (1891), Mary (1893), Michael (1896) and Delia (1898), and lived all his life in the townland of Ballymore, Co. Mayo. Enter all of this simultaneously into a query, and the possibility of getting a match is zero.
All it takes is a single missing item in the originals, (the page recording Michael’s birth was used to light a fire in 1898), a single missing item in the database transcripts (the transcriber had a late night and dozed off over the marriage record) or a single item misreported by the family (John was actually born in 1890) and the response from the database will be the same: no match.
Don’t get me wrong. Knowing these details will eventually help unlock the truth. But to start off, you need to cast the net as wide as possible. How many Brennan births are registered in and around Ballymore between, say, 1864 and 1870? How many Johns? Can you identify the precise marriage registration, using only the names, not the reported date? What are the ages given in the 1901 and 1911 censuses? Do they match each other, or the ages you think you know? (Unlikely.) Are there other Brennan households in and around Ballymore in 1901 and 1911? Any with heads of household of an age to be siblings of John?
The biggest sites – ancestry.co.uk, FindMyPast.ie, irishgenealogy.ie – all know that funnelling research like this, starting off broad and ending narrow, is by far the most productive way to use their records and have set up their search interfaces to encourage it. They know what they’re doing.
['Irish Roots archive from 2009 at www.irishtimes.com/ancestor/magazine/column]