Service tax for online services

Hi,

We are planning to launch some sort of online services soon and will be charging for customers for the same. My question is do we need to register for service tax right away or after crossing 8 lacs turnover in a financial year. Also suppose we cross 10 Lac limit do we have to pay service tax on all amount or on the amount exceeding 10 Lac. Also will really appreciate if somebody can explain procedure to get service tax number and expenses in that.

Thanks,

Ksh*tij