With the introduction of a pre-trading session starting Monday, trading in India is set to change forever. One cannot start trading until 9:15 am. Pre-trading session will be held from 9 am to 9:15 am.
Deena Mehta of Asit C. Mehta, who has been a strong advocate of a pre-trading session, says one will know the mood in advance and can plan one's strategy accordingly. It is a small move, but a very useful mechanism particularly on high volatility days. This will matter more when there are sudden major developments.

Other Pre-market opening features:
  • No entry, modification, cancellation executed
  • Orders accumulated for specified period
  • Price and quantity information is shared
  • Provisions to discourage manipulation
  • Limit and market orders is allowed
  • IOC conditions are not allowed
  • Iceberg orders are not allowed
  • Limit orders prioritised over market orders
  • Price banding at 20% applicable
  • Circuit filter for continous sessions only
  • Open market orders to move as limit orders at open price

Source : Moneycontrol