What is the best way to build your vocabulary?

I am trying to learn German, but I don't know where and how I can just learn random German words.

Any suggestions?

Yes. Open the dictionary at a random page and learn the first word you see!!

I use flash cards with a picture and the German word on the other side.

In my opinion, parallel texts are the easiest and most enjoyable way of absorbing vocabulary.

http://langwelt.phpbbsite.com/follow-up-to-the-listening-reading-method-t26.html

Thanks, JLK. As if you would randomly open up a page in the dictionary...

Where do I get audio?

German audio books? You'll have to register on that site and PM me. I don't really want to post my email on this forum.