Generally do not initiate the FIRST TRADE before 10.30 AM of the day since during the period 9.55am -10.30am the nifty uses to be highly VOLATILE and first trade is quite important as it is precursor of next few trades.Similarly do not initiate FRESH trades after 3.00PM and you can hold the futures/equities if already they are in PROFIT ,but need to be closed down before bell rings.