In every iteration, have a few bugs that do not get fixed. After five or six iterations you can build up a reasonable size bug backlog without even trying, and the best bit is that you can hide them in the previous iterations so nobody important sees them.
- If there is anything left over in the current iteration, move it into the next and increase the priority of that item.
- Review all items that overflow into the next iteration to make sure that the team understands what is needed.
- Publish the failure up the management chain if a defect survives to iterations.