I appreciate your caution and respect for the subject matter Richard, but when it comes to genealogy we needn't be shy about history; it's a major part of the story after all. :)
That being said, you will find that there is a unique situation surrounding records from before and after the creation of Northern Ireland, which I am happy to explain. ;)
Civil registration, as we know it today, wasn't introduced in Ireland until 1864. So right off the bat, all records from before that time would have been church or parish records. While some of these have regrettably been lost over the years, all the remaining records have been sorted into county based genealogical centres
, so this is the first place to turn to, in order to find documents and information for your ancestors, no matter what area of Ireland they lived in.
In 1864, civil registration was introduced, as I mentioned, and we seethe creation of the General Register Office of Ireland
(GRO). All records, including but not limited to birth, marriage, adoption and death certificates, have been kept there ever since. Now, in 1921, when we saw the official creation of Northern Ireland, we also saw the creation of PRONI, the Public Records Office of Northern Ireland
and this is where it gets interesting! The six counties of Northern Ireland were of course counted and treated like the rest of the island until 1921, so all the records for people born/living in those six counties before 1921 would have had their records stored at GRO, and only births, marriages and deaths from that year onward have been stored at PRONI.
In order to find the specific information about your family, I would recommend that you start by building a paper trail and then working your way back, until you know which of the above mentioned offices would be the most appropriate for you. The way to do this is by gathering as many documents as you can from your local registry office and archives, starting with your own birth certificate and then adding those of your parents, four grandparents, eight great-grandparents etc. until you come across your first ancestors who were not born in the same country as you, but rather, in Ireland. Once you know when and where in Ireland your first emigrating ancestors were born, you'll be able to select the best office.
Good Luck with your search! :D