Deadlock tracing

To trace deadlocks and report it to sql server ERRORLOG:
DBCC TRACEON (3604) -- report to log file
DBCC TRACEON (1204) -- trace deadlock

To switch it off:
DBCC TRACEOFF (3604)
DBCC TRACEOFF (1204)

To check which flags are on:
dbcc tracestatus(-1)

To cycle sql error log:
sp_cycle_errorlog