Service tax under .05 lac (below threshold limit rs 10 lac)

Dear Sir/Ma'am

I am an Architect by profession and got service tax registration number recently in January 2012, as it was mandatory for opening a current account. Now I have a project with INR 50 k paid by client without any mentioning of tax and this is the total turnover for my firm (proprietorship) for the financial year 2011-12. I am very confused about paying the service tax and filing the return on ST-3.

Please guide me through this, I have four specific queries.

1. What is the amount of service tax I need to pay If any and Is it to be done before March 31, 2012.
2. If this is NIL amount (considering total is less than 10 Lac), do I have to file ST-3 before 25^th April 2012.
3. Is there specific procedure to follow or form to fill for geting this exemption (waiver) of service tax?
4. Do I need to ask my clients for paying service tax after crossing the limit of my turnover by 10 Lac or it starts with first billing of any amount (Say 100 Rs.).

Waiting for prompt reply.

Thanks and Regards

Munendra