Permissions for directories?

Is there anywhere I can go to figure out what permissions I should have for my directories? I’m using godaddy shared hosting. I have one wordpress site on my root directory, and other sites in a /_sites/SITENAME directory, all with their own installation.

I’m just trying to cut down on some security holes, and I’m getting random internal 500 errors, so is there some guide or plugin that can help with what permissions I should have for each directory?