How to file nil svc tax return for sole proprietor

Dear Friends,

I recently applied for a Sole Proprietorship in October 2011.  There has been no income yet in our Services business till date (12-12-2011).  Two questions regarding filing ST returns:

a) When (and at what regular Intervals in a year) do I need to file a ST return?

b) In startup situations, where there is zero income, I am told i still need to file an NIL eReturn, but what specific steps do I need to follow to do this effectively. (e.g. which form - ST3? - and where do I go to file it..the ACES site seems vague on the specifics!)

Thank you all for your guidance and wisdom!