Zenimax Online will be sending out invites this month for The Elder Scrolls Online's soon-to-launch closed beta. So there's only a short time left to apply if you're wanting to be considered for this first round of selectees.
Further details and an appropriate video below.
Zenimax announced that they'll be sending out the invites through the time-honoured tradition of an FAQ which comes chock full of useful information like "beta events will generally be held on the weekends" and "Don't eat salt"*.
The important things to know are that you can sign up for the beta here and Zenimax will be sending out invites to the first scheduled beta event on the 28 March. Rather than having an ongoing beta which is steadily updated till release, Zenimax have opted for regular beta events. So don't expect to be getting to any of the end game content before the game's eventual release.
Now, that appropriate video.
*One of these facts may not be a quote. That, however, does not stop it from being true.