Getting experience is one of the catch
22's in most industries, but especially the game industry.
Companies want experienced people, but you can't get experience unless
someone hires you.
There are a number of solutions to the problem, but one way to build
experience is doing free work. In this case, doing free beta
testing.
The sites below maintain list of companies with open beta test.
Try a couple and get some experience. Make sure you submit
effective beta reports, perhaps even reports much better than the
company is asking of you. Who knows, you might even hire you
as a tester. But even if they don't, you have one more experience and one more
document to put in your portfolio.
http://betawatcher.com
http://fileplanet.com