deploying wabapps (e.g. moodle) on heroku

What is the proper way to deploy webapps on Heroku? I'm installing Moodle, but the same procedure should apply to e.g. Drupal or Wordpress. What I hace done is to unzip Moodle locally, then uploaded it using git to Heroku. When I then visit my site I get the option to install it and select the database, which works fine. The problem is that the install procedure saves information in the filesystem on the server, which gets overwritten next time I deploy my app. So what is the proper way of doing this?