First I'm not really sure there is an auto-update but my phone got updated to 4.1.2 and didn't purposely do anything to cause it, so wondering if there is a way to get a yes or no prompt or something similar?
There are no native settings to control OTA updates. Typically when there's an update available you'll get a notice and have the option to accept, defer, or reject (see Software Update Instructions on Verizon's Software Update page here: Software Update: Galaxy Note? II by Samsung - Coming Soon! | Verizon Wireless). Deferring or rejecting will only forego the update for a certain time period. If you don't happen to catch the next prompt to defer or reject again, it will automatically try to download and install the update. The only way to fully stop this and give you some level of control requires that you root your phone and disable the OTA updater. Frankly, IMO this is one area Android needs to mature in and provide us more control without requiring root. Example: like in Microsoft Windows where you have the option to set software updates to: Automatic, Notify only, or Disable (manually install them if and when you want).