Irelands largest Airports are Dublin Shannon and Cork in that order. Ireland is well served by air routes from the UK and Northern and western Europe. The amount of routes to southern and eastern Europe is growing. The largest and lowest cost airline serving Ireland from Europe is Ryanair. The other main Irish airline is Aer Lingus.
For visitors from outside Europe the cheapest way to get here tends to be via London, all the major Carriers offer regular scheduled flights to London with connections to Ireland via their alliance partners. During the peak season a number of smaller charter carriers tend to offer flights to the UK from world wide destinations and these are often cheaper than the regular flights.
If you fly to Dublin or Corkyou can get trains or buses to Kerry. In general the west of Ireland is not well served by public transport and since many of the most interesting sites tend to be a little off the main roads.
If you do hire a car a good map is a must and it is usually worth while to get an up to date guide book if you plan to visit regions not covered by your own research. Also bear in mind the Ireland is in principle a bilingual nation so you will see road signs in both English and Irish (Gaelic).