One of the most important pieces of information in order to be successful researching your ancestors in Ireland is the name of the townland where your family lived. This is the most difficult piece of information to find…depending on the timeframe, most records in the United States will say just "Ireland." Having said that, you have to search all records left by your ancestor, all family members, witnesses, neighbors and others they associated with in order to find the information.
Once you identify the townland, you can use the General Alphabetical Index to the Townlands and Towns, Parishes and Baronies of Ireland to identify the civil parish, barony and Poor Law Union to find various records in Ireland. Another place you can check is the Placename tab of Irish Ancestors. If you're lucky, you can put in the placename and come up with the County, Civil Parish and Poor Law Union. Unfortunately, a lack of creativity in the names of the over 60,000 townlands will likely provide you with multiple localities of the same name, sometimes even within the same county.
Perhaps you have a townland name, but are not sure how it's spelled. Locality names passed down over the years may have become distorted, or you might have the classic problem of an illiterate Irish immigrant providing the information to a German census taker. Using the Advanced Search feature you can use a wildcard search to find the correct spelling. A "%" can represent any sequence of letters, or a "_" can represent one letter. There are thousands of townlands beginning with Bally (from the Irish Báile, meaning town or homestead). Hopefully you can pick out at least the letter following Bally. A client provided me with the townland name of Ballynedretich which she knew was in Antrim in the parish of Killead. The spelling provided no match. A search on "Ballyn%" in the placename field, adding the county Antrim and the parish "Killead" in the Advanced Search, provided two possibilities: Ballynadrentagh or Ballynageeragh allowing me to select the correct townland.
If you are having a problem finding a particular location in Ireland, give this a try. It is another free resource on Irish Ancestors.