I have done GA tickets a few times. It's an amazing experience. You will discover Facebook groups and Twitter feeds about "the list." I have never used that process, I've just shown up at the shows. I walked into MetLife Stadium around 5:30pm and was one person from the rail. I spent most of the day in Dublin waiting near the stage and by 4pm, was somehow moved further away. No matter where you are - at the rail, near the soundboards, or somewhere in between - it's an amazing experience. Don't stress it, just enjoy.