The official Star Wars Galaxies homepage has updated their FAQ to reveal information about how beta testers will be selected. Here's a quote:
There are many factors in selecting potential first round beta testers. In the process of trying to make the best possible use of test, we will primarily be hand-selecting people from our community. Beta selection will not be based on number of posts. Please do not be discouraged if you are not selected for an early Beta. Eventually everyone will have the opportunity to participate.Click this link to read more.