Verizon Galaxy Nexus users, you finally have the Android 4.0.4 OTA update coming your way. You were one of the first to own a Galaxy Nexus (see our detailed review) and experience Ice Cream Sandwich, and yet now you're one of the last to receive updates (after GSM and Sprint LTE). Yup, the previous update, ICL53F, was in... December of last year. I know how bitter it makes you, and I don't really have excuses on Verizon's behalf, so let's just get down to business.
Note #1: First of all, the bad news - if you're not rooted or don't have a custom recovery, you will have to wait for the OTA. There's no way to manually flash update files with full stock, which is definitely a bummer, but unfortunately it's true. The good news is that you won't have to wait long - there are plenty of people who already received theirs, and yours is hopefully somewhere in the queue.
Note #2: Secondly, the update is rolling out to users running 4.0.2 (ICL53F). If you've flashed manually to the previous 4.0.4 leak (IMM30B), these instructions will not work for you - you'll have to either go back to ICL53F, wait for the full 4.0.4 OS image to show up at the Factory Images page, or find an update file that specifically targets IMM30B.
Image credit: krazie1
Update 5/23/12: Google removed the OTA from their servers shortly after they put it up May 1st, but just now put it back - exactly the same as before (I verified the MD5 signature). What an odd move. My guess is they rolled it out to some users, then started examining their reports but found nothing wrong, so the rollout of the same build was resumed. Hopefully, this means the OTA to non-rooted users without custom recoveries is going to start soon.
So, if you're running ICL53F and are either rooted or have a custom recovery, carry on.
Rather than provide the installation steps here, I'm going to refer you to this XDA post which contains excellent instructions for every combination of recovery and root status you can think of.
More info at XDA