Quoted from the movie The Matrix "More important than what is when"
This post is about letting everyone know that you can transfer to any US world in Guild Wars 2. But the time to do it is the most important thing to know. It's on Sunday evening after 7:00pm Pacific Standard Time. It's probably good until about 10:00pm Pacific Standard Time. This means NOW is the time to do your transfer if you want to get to a world that is normally FULL.
Any other time and some worlds are FULL, you can't transfer to FULL worlds as noted in the list. At the bottom left of your character select screen is a button with the label "World Selection". Press that button and you can do your account transfer to any world in the list at this moment in time. HIGH worlds can be transferred to, but FULL worlds cannot.
Keep in mind that if you want to do World PvP, it's not a good idea to be on a world that is FULL most of the time because the queue time to get into the battle will be longer than for a MEDIUM world. However if you want to be on a world with your friends and you can't do your transfer, wait until the evening on Sunday when most players are not online. Having said that, there is no cost at the moment to do a world selection transfer. But ArenaNet will soon be applying a cost to that option.
It goes without saying here because of other posts in this message forum that most Oceanic players are playing on US worlds. This is the primary reason why Sunday evening after 7pm is the ideal time to transfer because there are much less players online until the Oceanic peak times start to come in.