I can't tell you how to win a duplicate tournament, but I can tell you a sure win to lose: underbid. If you bid one level lower than everyone else, and they all make their bids, you will get a 0% result regardless of the bag situation. Underbidding to an 11-total has another drawback as well. Your partner will likely try to bag even when a set is possible.

Q9653 1053 AKJ107 -- K7 Q95 Q532 K1065 84 AK42 964 A842 AJ102 J87 8 QJ973 East South West North 3 2 2 4 South led the Q

There is no justification for North's 4th-seat 4-bid. The hand is worth a call of 5 in any form of the game, and a 6-bid should be essayed at duplicate.

With all four hands in view, we can see that East/West can score a maximum of four tricks -- three hearts and the spade King. They get no clubs so their 5-bid is doomed. In the play of the hand, however, North and South contrived to make their 6-bid exactly (I'll skip the gory details) and so they scored their 60 points. Seconds later the board's results were posted: a cold bottom. Played seven times, every other North/South bid at least 7 and proceeded to set their hapless 5-bidding opponents, scoring at least 118 points
(70+50 - 2 for bags). Even if our conservative North/South pair had played for the set, they would get only 107 points (60+50 - 3 for bags) and still bring up the rear with a 0% result.

I am not advising everyone to overbid at Duplicate Spades; but for heaven's sake, don't torture your partner by underbidding.