I tried pathauto before on another site, but I couldn't enable clean urls back then. Luckily this time it went smooth. I installed the modules pathauto, token and path. I enabled clean urls and this time the test went without a problem.
For the configuration of pathauto I googled and found these two links:
I think I'll need some more time to master the configuration options completely. Just one question for the drupal ninjas: how can I generate a new alias for story. As I have already one alias for my first story, but I didn't like how it was build and changed the pattern.