Put the ring in a small box filled with 4-leaf clovers and give it to her on St. Patty's day for extra good luck. You can buy genuine four-leaf clovers online at fourleafclover.com
Give her a four leaf clover locket with a small note saying inside the locket that says "Will you marry me?". Put the ring on the necklace chain or present it to her after she's opened the four leaf clover locket.
Attach the ring to a four-leaf clover key chain and have it waiting for her in her purse... or in the car ignition when you're on your way out to dinner!
Take her out for drinks and fun at a local Irish pub and propose as you celebrate in green.
Have your sweetie search for her own lucky pot o' gold! You can fill a small pot with golden chocolate coins (found at most candy stores) and a ring inside. You can either leave the pot o'gold out in the open for your sweetie to find or leave clues filled with romantic notions leading them to the end of their rainbow.
Celebrate the day at a St. Patrick's Day parade. Arrange ahead of time for one of the floats to be carrying your proposal along and when it arrives in your area, get down on one knee and propose.
Take her out for a traditional Irish dinner or corned beef and cabbage at a local Irish restaurant. As you enjoy your dessert, surprise her as you get down on one knee and pop the question.
Prepare a traditional Irish dinner at home and eat by candlelight as you sip your Guinness. As you finish up, ask her to make you the luckiest man in the world by becoming your wife.