Sexing my beardie

So I've had my beardie for about a week and I was wondering how does one tell what sex it is? The store help called him "He" so I went with that but I would really like to know for sure.

http://www.beardeddragon.org/articles/sexing/

This is a great link showing how to, but depending on how old your beardie is, you may not be able to tell just yet.

Thanks. That link was great. He is too young to tell at this moment but now I know what to look for.