How to get to Dublin
Dublin airport is serviced by most large airlines, however excellent deals can be found using Ryanair and Aer Lingus, the two main Irish carriers, especially if you book well in advance. Two brilliant flight search engines that might help you plan your trip are Skyscanner and Hipmunk.
There are also many ferries from the UK, France and Holland to Ireland. Check this site out for more info: http://www.ferry.ie.
How to get around Dublin
Dublin is pretty small. The city centre is easy to get around by foot but should you want to go further the DART (green train serving suburban Dublin along the coast), the Luas (inner city & suburban tram network) and Dublin Bus (city and suburbs) are pretty easy to navigate around.
How to get around Ireland
The easiest way to get a round Ireland is by train. It’s not too expensive (cheaper if you book online and in advance) and is pretty fast. Check out the website here: http://www.irishrail.ie. Rural buses are cheaper but take quite a long time – www.buseireann.com. But you can also get direct buses for quite cheap. There’s a variety of them – Go Bus, Aircoach & Citylink.
Finally, renting a car often makes everything easier. Details here: http://www.irelandcarhire.com.