The first question asked by anyone embarking on ancestral research is "What do I need to know before I start?" Unfortunately, there are as many answers as there are families. Although research has its pleasures, in genealogy it is better to arrive than to travel hopefully. You can start from your own birth and work back through records of births, marriages and deaths, parish records and census records, but in practical terms the more you can glean from older family members or from family documents the better: there is no point in combing through decades of parish records to uncover your great-grandmother's maiden name if you could find the answer simply by asking Aunt Agatha. Nor does the information you initially acquire this way need to be absolutely precise. At the outset, quantity is more important than quality. Later on, something that seemed relatively insignificant - the name of a local parish priest, the story of a contested will, someone's unusual occupation, even a postmark - may well prove to be the vital clue that enables you to trace the family further back. In any case, whether or not such information eventually turns out to be useful, it will certainly be of interest and will help to flesh out the picture of earlier generations. For most people the spur to starting research is curiosity about their own family, and the kind of anecdotal information provided by the family itself rarely emerges from the official documents.
To use the record resources fully and successfully, three types of information are vital: dates, names and places. Dates of emigration, births, marriages and deaths; names of parents, siblings, cousins, aunts, in-laws; addresses, townland names, parishes, towns, counties . . . Not all of this is essential, and again absolute accuracy is not vital to start out with. Indeed inaccuracy is more often the rule than the exception in family lore. So a general location and sibling' names can be used to uncover parents' names and addresses, and their parents' names. A single precise name and date can be enough to unlock all the other records. Even a name alone, if it is sufficiently unusual, can sometimes be enough. In general, though, the most useful single piece of information is the locality of origin of the family. For the descendants of Irish emigrants the locality is often one of the most difficult things to discover. There are a variety of ways of doing this, however, both in the records of the destination country and in Irish records online. The best time to do it is certainly before coming to Ireland. A guide to staring research online is here, along with the most useful Australian, North American and British sources for uncovering the locality of origin of Irish emigrants.
The only absolute rule in family history research is that you start from what you know, and use that to find out more: where your research leads you will depend very much on the point from which you start. So, for example, knowing even roughly where a family lived at about the turn of the century should allow you to uncover a census return. That will include the reported ages of the individuals, leading to birth or baptismal records giving parents' names and residence. That should lead to a marriage record, supplying fathers' names from the preceding generation, leading on in turn to early parish and land records. Those in turn may lead back to census records of extended family members. At each stage of such research the next step should always be determined by what you have just found out: each discovery is a stepping-stone to the next, another thread to follow. As a result, it is simply not possible to lay down a route that will serve every researcher. It is possible, however, to say that there is no point in taking, say, a seventeenth-century pedigree and trying to extend it forwards to connect with your family. Although there may very well be a connection, the only way to prove it is by expanding your own family information and then working backwards.