I have to go for h1b stamping in chennai india.wanted to know what is the start date of stamping and how much time before we need to take the appoinment.As my employer is telling they will take the appoinment 2 weeks before,can anyone pls help.

If your H-1 petition is already approved, then you can appear for visa stamping at the earliest available date. The visa stamp itself will be valid from Oct 1 or actual stamping approval date (whichever is later).

DO you have any idea how much time before we have to take appointment for stamping

There is no wait time. You can take the appointment even now provided you have all the necessary documents.

Slots are available based upon demand. At the moment, there is a wait time of 2-3 months at most of the consulates in India.