Here are some tips:

1. Never update unless you have a clear understanding of what you are updating to.
2. ALWAYS, ALWAYS, ALWAYS do a manual backup of your data before doing any update.
3. Never do an OTA update. Just don't. Use a computer.
4. If you insist on updating OTA, follow number two above first.
5. Understand what happens when you do a device update in terms of applications.