Just a quick one - don't forget that SQL Server isn't the only source of deadlocks. I recently helped out on an issue where a single-threaded application DLL on one thread was blocked by a SQL Server lock, but at the same time, access to the application DLL from the locking process was also blocked. No deadlock victim, just timed-out queries and a lot of pain to the system's users.

Classic deadlock... but only one of the locks was within SQL Server. 1204 is great, but troubleshooting SQL Server deadlocks is simple compared with tracking down the problem I was helping to diagnose.