[development] Theming views output in Drupal 7

Hi, I have tried to use the old Drupal 6 approach to theme views output, such as rows and fields, that is creating the suggested template file in my theme and adding the appropriate THEME_preprocess function to template.php. In Drupal 7 this doesn't seem to work. Although my template file is picked up, I can't use these preprocesses. Could someone help me out and explain how this should be done, or point me to the documentation on this? I have tried using hook_theme to register my preprocesses, but to no avail. Balazs