Source: [ilink url=”http://www.acbl.org/”]2006 ACBL Bulletins[/ilink]
A two-way guess for a missing queen often begins as a 50-50 proposition, but a capable declarer will guess right at least 75% of the time by constructing the defenders’ hands, using clues from the bidding and play. Test your queen-placing in
the following problems. IMP scoring.
West leads the 
J, and East takes the K and continues with the A. Who has the 
Q?
Each defender has one of the missing high diamonds. If East had both he’d have opened the bidding; if West had both, his opening lead would bave been a high diamond. Since East would have opened the bidding, especially in third position,
with the A K, a diamond honor and the Q, West has the Q.
West leads the 
K and shifts to a trump. You draw trumps, finding East with J-9- 8. Who has the Q?
Each defender has a high heart. If East had both, he’d have responded to West’ s opening bid; if West had both, he’d have shifted to a high heart at the second trick. Since East would have had enough points to respond to the opening bid with a
heart honor, the J and the Q, West has the Q . When South get around to playing the clubs, he’ll probably lead theJ for a backward finesse. When West covers, South will take the ace and return a club to his 8.
West leads the 
Q, and East takes the ace and shifts to the 10. West takes the queen and ace, East showing out, and leads a third club that East ruffs low. Back comes a low heart, and you take your king. Who has the Q?
East had one club. He has at least four hearts to respond 1, but can’t have more than four since West needed three cards support to raise. Since neither defender bid spades, they’re likely 4-4. Play East for 4-4-4-1 distribution. Lead to the A and let the 9 ride.