How can I avoid that users vote for their own posts?
The rate module allows you to do this in its settings. You have to create a widget for this : admin/structure/rate (just add a new one and then you'll see the option). 
You will be asked to choose the content type and the position of the widget in the page that you need to define to see the vote system. I didn't try nor with views integration, neither with Drupal 6.