Hi all,
According to the zenphoto installation readme, permissions for 'albums' and 'cache' directories - and I assume subdirectories within them - need to be set to rwxrwxrwx (777).
How about the rest of the files in the zenphoto package - what permissions should they have? (My question may seem dumb to some but, hey, I have to start somewhere!)

You just need to chmod the cache and the albums directories. Nothing more :-)

But just as a general rule, they should have 644 permissions (rw-r--r--) for general HTML and images and PHP files. Directories should be 755 (rwxr-xr-x) in general.

Many thanks to both for your helpful replies!