Last Updated: November 13th, 2012
If you want to update your Nexus 7 to official Android 4.1.2 that started rolling out earlier today but your turn hasn't come yet, you have two options: wait (possibly for a while) or flash it manually. The latter is absolutely safe and lets you bypass the line without any risk whatsoever. Even better - you don't even need to be rooted or running a custom recovery - updating with Jelly Bean and full stock recovery is easier than ever before.
Last Updated: December 21st, 2012
If you're going to be messing around with custom ROMs at all, it's a good idea to have a nandroid backup at the ready. A recent backup can save you a lot of time and heartache if things end up going sideways. However, backing up your system used to mean rebooting into recovery and waiting for 5-10 minutes while everything progressed. That's not the end of the world, but every barrier to backing up makes people less likely to do it.
Last Updated: October 3rd, 2012
After upgrading my Galaxy Nexus (GSM) to Jelly Bean last night (I know, I know, I'm a few days late), I unlocked its bootloader (the usual fastboot oem unlock) and commenced rooting, which I thought would only take a minute or two. However, after almost 2 hours of pushing, flashing, rebooting, and trying no less than 5 different root methods, I still didn't have root. Something must have changed under the hood, and no root method I was trying was working (even PaulOBrien's SuperBoot).