Decide which part of the country you want to make your "home base" for the duration of your vacation. Choose a destination that is close to the attractions you plan to visit, but also gives you the opportunity to venture out and discover new things if the mood strikes.
Know the lingo. Instead of going on vacation, the Irish go "on holiday." Many companies offer apartments, cottages and even castles for rent under the description "self catering." If you're looking to rent a car, look for advertisements about "car hire." Understanding the terminology will help you navigate local web sites.
Research rental companies to find one that is reliable. Look for recommendations from trusted travel web sites, or stamps of approval from local agencies.
Compare the prices of the different agencies that offer cottages for rent. What amenities are included? Do you want total authenticity with a peat fire and a thatched roof? Would you prefer a cottage setting but like to have some modernized comforts as well? Read the listings carefully for these details.
Read rental agreements before signing a contract. Be sure that you understand what is expected of you and what you can expect from the rental agency. Pay special attention to when your deposit and final payments are due, and determine what the penalty will be if you need to cancel your trip.