Hello Subramanyam,
Going by my experience, you will have to first open an account with the a brokerage firm on their standard brokerage rates. Later, when your activity in the stock market increases, increasing your daily turnover, you can bargain for better brokerage rates. Therefore, go ahead and find yourself a broker keeping in mind the parameters suggested above and then bargain for better brokerage rates after a month or a quarter down the line.