My employer has received the H1B petition.and given me the original documents.
What should be my next step.
The VISA stamping is done on passport ?
When would the stamping process be initiated ?
What are the qusetions generally asked during stamping anf how much time it takes for the actual stamping to happen ?
Ask the employer or attorney to send all the documents to you. It will be bunch of around 150 pages (1.2Killogram 
). Normally, only photocopy of I-797 is necessary but Indian consulates sometimes ask for original so it is better to get all the originals. Once you have the documents with you, follow following.
Create a new application for DS-160 at Nonimmigrant Visa - Instructions Page
Fill all the information
Once you are satisfied that it is completely filled, confirm the application and take printout of the confirmation
Now, go to ustraveldocs.com
Create a account by signing up
Take an appointment. During appointment process you will have to pay the fee 190$ (around 11,780 Rs.). You can either pay using NEFT, IMPS or visiting the bank (The fee you can pay before taking the appointment also).
Fee is a separate process and is not linked to any application directly. So, it is important you keep safe the transaction number/ reference number while making payment through NEFT/IMPS. It takes few hours receipts to become valid at site so be patient.
Once you have fee reference number , type in the payment page and click continue.
Take a date of appointment. You have to take 2 dates. One is for OFC where your photo and finger prints will be taken. This should be before the date of interview ( Well, interface makes it sure that you don’t mess it up but still take care of it because you need atleast 2 days)
Appear in the interview. if interview goes well he will take your passport. The passport will be mailed to the selected office ( you choose it while taking the appointment) after stamping.
Best of luck !