1. Stay calm
2. Take a few minutes to read read the threads & posts already made
3. Add your post to the appropriate thread including as many details as possible, e.g. What is the nature of the error? What steps did you follow before it happened? Which city and venue you were buying tickets; Which zone and section were the tickets you were buying? What device are you using - computer, a tablet or a mobile phone? etc.
4. If you don't want those details public, PM mods @Max Tsukino, @mich40 or @bigwave who are around all presales
5. Add screenshots if possible
6. Check if your code is the correct one for the appropriate presale group. If it starts with U2JT9A..., You are on the Red Hill group. If it starts with U2JT9B..., You are on the Wires group.
7. Don't multi-post the same issue, try to keep on-topic
8. Make sure you only use links from U2.com/tour
9 READ Tips 1-7
10. Share your tips & scores too with the rest of us