Go for one that is a member if either the IAVI or the IPav - they will probably be more qualified.
These days - especially if you want the widest exposure for your house - you probably have to go with an auctioneer who is with Daft.ie or Myhome.ie or both .
Also if an auctioneer's website is high up on google - that in my view would be good. Try "houses for sale in Kilkenny" or "property for sale in Kilkenny" on google and see which auctioneers appear n the top 5. If you can find them easily - so can the potential buyers.