As a genealogist, one thing I have to be constantly aware of is variant name spellings. There is nothing worse to me than having spent an hour searching a complicated name index for several variants, only to get to the end and realize I forgot one variant of the name. And then have to go back through all over again. It is such a time-saver to search for all of the possible variants the FIRST go-around.
If you have Irish ancestors, you are in luck. I recently learned about a great little research aid on the IrishTimes.com website. At this site, just type in a surname and find out, among other helpful things, all of the variant spellings and associated names for that surname! In my opinion, this is especially helpful for Irish research because sometimes I would NEVER be able to guess the possible variant names. Thank you Irish Times!