[support] Permission question

During my first Drupal site build process, I received quite a few error messages, and I made a lot of stuff to 777. 'files' directory is one. 'modules' directory is another. You might remember I had 99/99 problem that won't let me chown, and file upload silently fail.

Now before I go live, I want to make sure all the permissions are set correctly. Other than settings.php permission setting, I can't find any mention of what others are supposed to be. Is there any list or general guide about this somewhere? I experienced a lot of stuff just don't work if 775, which is kinda puzzling.

I think my most concern right now is 'modules' directory, which I think I messed up the permission.