This is the same answer that I gave to someone who was going on their first testing interview; copied and pasted here to save time while preserving its value, I hope.
If you've never done software testing before, it would be a good idea to learn some things quickly.
I'd recommend checking out the Black Box Software Testing course, available free (without an instructor) at http://www.testingeducation.org/BBST, or in an instructor-led version that is free to members of the Association for Software Testing (http://www.associationforsoftwaretesting.org). This is a university-level course, hours and hours of video, supplementary materials, quizzes, self-tests, and pointers to other information.
James Bach and I co-author and teach a course called Rapid Software Testing (http://www.developsense.com/courses.html). The course notes for that are available for free at James' Web site, http://www.satisfice.com/rst.pdf.
I've written a lot of articles on testing for Better Software magazine. They're available free at http://www.developsense.com/publications.html.
In addition, there's a blog post for you: http://www.developsense.com/2009/02/how-can-trainee-improve-his-her-skills.html
There are several testing communities online where you can ask questions and get mentorship. http://www.softwaretestingclub.com and http://www.testrepublic.com are two of them.
Best of luck.
---Michael B.