With alpha testing finishing around the end of June 2010, beta testing is expected to begin in early July. The beta stage was originally estimated to last around six months, but with the game announced as a September 22nd/30th 2010 release date it would seem this estimate included the alpha.
The alpha phase of the testing was conducted in small groups participating in 3-4 hour tests to see how the game performs. After this came the beta, where the plan was to hold weekly 24 hour tests after stabilising the servers. The third phase of the beta started on August 11th 2010 and will be the final phase of the closed beta. After this an open beta will take place, which is likely to be a stress test designed to see how the servers will cope with tens of thousands of users accessing them at once.

On December 16th 2009, Square Enix started taking applications for the beta. Applications are for both the PC and PS3 versions but only the PC version will be tested at first. Successful participants will be notified via e-mail.
It is not necessary to re-apply for each round of the beta; your original application will remain valid throughout. We advise you to only apply once, because if you are found making multiple applications you will be denied access to the beta.
The deadline for closed beta applications was August 16th 2010. With September 2010 came the open beta, where anyone could sign up, get a beta key and play.
To sign up for the open beta you will need to go to the following page:
http://entry.ffxiv.com/
Details of the Playstation 3 beta will be made available at a later date but it is expected to begin after the release of the PC version.