First of all, congratulations for getting into the beta. We all want Guild Wars 2 to be perfect, right? Well, nothing is perfect so let's try to make it the best we can! When you're in the beta and the little Survey comes up, FILL IT. It doesn't take more then a couple of seconds. If you encounter a bug or a badly designed dynamic event, REPORT IT. If you think a class is too powerful, REPORT THAT ASWELL. This is not a demo, it's a beta and you should treat it like such. Let's all come together and make this the best game we could possibly have!
Oh, and don't break the NDA either.