Service tax return

One of my frined have been applied for Service Tax Number and same has been issued on 21st December-2012. His sale/Bill as on date NIL. I want to know :-

1. NIL return is mandatory ? If yes what is the last date of Filing return ?

2. If anybody applied for Service Tax Number and after issuing the ST Number it is mandatory to add service tax from First Bill ? or will be add after 10 Lakhs in same Financial Year.

Thanks for your Co-Operation in advance.