First, request the surname index for the county for which you are interested. Usually, there are from two to six microfiche for each county. The beginning dozen pages of the first microfiche will contain useful introductory material relating to Baronies and Parishes (Civil and Religious).
After the introductory material, you will see a table that looks like the following (there will be two tables on each page):
Abbott G T Fermoy
Abbott G5 T Barrymore
Adams T Condons
Ahern G22 T Imokilly
Ahearne G T Barrymore
Ahern G9 T Kinnatolloon
This is the alphabetical listing of surnames and the baronies in which they occur. The G indicates that the name occurs in Griffith's Valuation, together with the number of occurrences in a particular barony (a G with no number indicates one occurrence, and the absence of a G indicates no occurrences). The T indicates that the name occurs in the Tithe Applotment Books.
Search this table for your surname and be sure to write down all information: the name, the G and the number, and the barony. Also, be aware of spelling variations; for example, note the spelling of Ahearn in the above table.