The following is a list of some of the recommended things to bring:
Your valuable printed information from visitireland.com
Other travel guides
visitireland passport
Passport (even if you don't need one)
Driver's license and other forms of identification
Credit cards, bankcard, cash and/or travelers checks
Camera and film
Address book
Cosmetics and toiletries
visitireland passport
Extra eyeglasses and contacts
Any necessary medicine (carry it with you personally with the prescription labels)
A waterproof jacket, windbreaker or raincoat
Two pairs of comfortable shoes
Umbrella
Watch
Travel Alarm
Motion sickness, upset stomach/anti-nausea medicine, and pain reliever
Chewing gum for ear discomfort (if you're flying)
If you are an American and want to be duly noted as such wear a pair of shorts, tennis shoes and a ball cap. It will be a dead giveaway.