You've heard the old saw "drive defensively". Well code defensively.

• Assume that all data is CRAP
• Assume that all code is broken. Especially if you wrote it.
• I don't give a hang what DRI is in place you can still have orphans and invalid data in tables.
• "That can't happen." is most often heard right after it just did.
• Code, reports, etc. that work just fine in the shop can and will drop dead upon deployment.
• Managed code is managed but not perfect.
• Even Micro$oft has bugs.

One of my customers switched to a large famous ERP system. The new system had been tested for months. What brought it down on the first day live? Someone posted a memo stating that all users should log on at precisely 10 AM Eastern. :w00t: Jammed the logon queues and, a couple of minutes later, the phone system. Perfectly working software. Killed by several thousand people all watching the clock tick down and hitting the button together.