Well, maybe not secrets, but lesser known troubleshooting steps and help for Xbox 360.  I’m learning way too much about this lately.

• Clearing your update cache:  This clears out the cache of dashboard, system, and other updates in case something gets glitched and you can’t update.  Go to the System blade, then select “Memory.”  From that screen, select your hard drive, then hit “Y” to get to “Device Options.”  From there, use the controller to enter: X, X, LB, RB, X, X.  You’ll get a message asking if you want to perform maintenance on the device - select Yes.  This didn’t do anything for my latest problem, but it’s worked for some people.
• Manually update the dashboard:  Deep in the bowels of the Xbox Support site they have instructions on how to download and burn your own dashboard update CD. I tried this but was never able to get it to work; that said, I already had the update the disc contained, so maybe it didn’t try to re-apply.  Xbox Support will recommend this to you if you’re having trouble taking an update over the network.