Here's just what I know from having a father and mother from Ireland and living there.
The priest that presides over a wedding is invited to the reception.
Mead wine is served, warm, at weddings. Usually the wedding cake is a lot like Christmas fruit cake. It almost always has fruit.
If a fork falls off the table a woman is coming to visit; a knife means a man.
When you have an itchy nose you should playfully hit everyone you are with and say "itchy nose" to insure you won't get into a fight with them.
Instead of playing "Punch Buggy" Where American's say "Punch buggy [colour of the Volkswagen Beetle that they see on the road], no punch backs!" Irish people say "Yellow registration, no returns". Yellow registrations are a type of license plate on cars in the United Kingdom and every so often you see one in the Republic of Ireland that are from Northern Ireland.
When there is an electrical storm, you should cover all the mirrors in the house or turn them around.
Your 21st birthday is the most important birthday. It is when you are considered an adult and it is a tradition to be given "the key to the house". Some 21st birthday cards still have keys on them as the symbol.
Irish dancers must wear their hair in curls.
On St. Stephen's Day, the 26th of December which is known to the English as Boxing Day, Irish children dress up and go door to door singing and performing. Sometimes they are given money, cookies, cake, tea, oranges, or nothing at all.
Also, common things that of as Irish but really are not: -Corned beef -Kissing the Blarney Stone (mainly a tourist attraction).
storytelling and music. Sport also very popular including indigenous games such as Gaelic football, and Hurling (relative of hockey) You got to have a pint in a pub bearing your name, though anything similar will do.
Not too sure about the list of stuff at the top there. I have lived in Ireland all my life and only a handful of things are really true. If I hit someone and said my nose itched, they'd punch me in the nose first before beating me to the ground and suing me.
But as far as sport goes, we have hurling and Gaelic football (Look them up). Cutoms? Umm.. don't think we have any really. Although if you call an Irishman English, it's a common custom for us to beat you to death. We have our own types of music (Sean nos, ceili, jig, reel) but, unlike what Americans think, we don't just listen to "Irish music". We aren'tt really that traditional but in some parts of Ireland called "Gaeltacht", they will only speak the Irish language (known as Gaelic or Gaeilge) to you.