1 Name, email, and country mandatory
There are fields on the join form that you do not need to fill in before submitting (such as "site" and "comments"). However, your name, a valid email, and your country must be filled in or selected in order to be added. I also ask for no names containing numbers, obscenities, etc.

2 A link back to this site is mandatory if you join with a website
You can supply either a text link or use a code/banner to link back. Also, the direct URL to the page containing the link (if you put in on a "fanlistings" page, for example) is needed under the "Code URL" field on the join form when joining.