Looking for the names and old address of your great-great-grandparents from County Tipperary? Though each county has its own archive, it’s more sensible to start tracing your Irish ancestry in Dublin at the General Register Office (Joyce House, Lombard St., Research Room, 2nd fl., tel. 01/635-4000, 9:30am-4:30pm Mon.-Fri.), where you can look up your ancestor’s birth, marriage, or death certificate (all of which should list the addresses of the parties involved) no matter which county he or she came from; the records here start at 1864. The fees are nominal, though they can start to add up if you need to broaden your search: €2-4 per request (you can request up to five annual record books at a time), and €4 for a photocopy. Though the archive is always a hive of activity, the staff is willing to answer quick questions and offer search tips.
You can also check the census records and various databases at the National Archives (Bishop St., tel. 01/407-2300, 10am-5pm Mon.-Fri.). Another good starting point, particularly if you need help planning your search, is the National Library Genealogy Advisory Service (Kildare St., tel. 01/603-0200, 9:30am-5pm Mon.-Wed. and 9:30am-4:45pm Thurs.-Fri., plus 9:30am-12:45pm Sat. Mar.-Oct.). This office has a few databases on offer but is worth a visit mainly for the knowledgeable staff, who will provide you with thorough advice. No appointment is necessary.
The General Register Office in Dublin has birth, marriage, and death records for the Northern Ireland counties as well, but there is additional information available at the Public Record Office of Northern Ireland (66 Balmoral Ave., tel. 028/9025-5905, 9am-4:45pm Mon.-Wed. and Fri., 10am-8:45pm Thurs.).
If you don’t have the time to conduct extensive genealogical research, consider hiring a professional. Ask at the National Library office for a list of private researchers; most are based in Dublin.