Many websites provide route planning services, among them:
The AA Ireland site at aaireland.ie (go to Route Planning) and Opel Ireland's opel.ie (go to Travel & Leisure).
Just enter starting and finishing points for your journey, along with any diversions you might make on the way. Then hit GO for a personal route map, with detailed directions, distances, and even how much it will cost you in fuel.
A couple of these done out in advance of a holiday or a business trip abroad can make things much easier right from thetime you set off from an unfamiliar airport.