I am planning a visit to Ireland from the US in September, what do I need?

just get a tourist or holiday visa and that should be good for you as regards immigration wear warm clothes if you plan on seeing crowe patrick or any of those sites wellies are a must also bring some going out clothes obviously you are but dublin and galway both have terrific night lifes i should know i am a college student in dublin and from galway great cities also the legal drinking age is 18 so you should enjoy that