Source: September 2016 ACBL Bridge Bulletin 
Some restraint, please
South opened 1 and West over-called 2. North chose to double, keeping hearts in the picture. South noted his K was probably not worth much and rebid just 2. North had enough to raise and South went on to game, although with mild apprehensions.
West led the K and East played the jack. What should South be thinking?
South can see he has a club loser, two diamond losers, and one or two heart losers depending on where the king is. Game isn’t going to make without a little luck. South is going to need the heart suit to provide tricks if 4 is to come home.
South should not take the first trick for many reasons, most importantly is that if he does win the first club, West will be able to put East in with a club later. East’s J promises the 10, so there’s a marked danger if South takes the first trick. South doesn’t want East on lead.
West continued with the Q, which South took. South led the A, everyone following. Because he needed something good to happen in hearts, he led one. What is South intending to do with the heart suit? South plans on finessing the queen. If it wins, as it must if South is to make 4, South must still play carefully. If he continues with the A and a third heart, either now or later, East may be able to get in with the J and will return a diamond, which will kill 4.
On the heart lead, West plays the king. Does this make life easier for South? Yes and no. At least West has the king. But South still isn’t home. He needs to set up another heart trick to make 4 . So how does South do that? South must let the K win. If West has a singleton K, he will exit with a club or a spade. Most likely it will be a club. South ruffs and plays another round of spades, both defenders following. The trumps are gone and South can now claim. When South leads a heart, West shows out, and South sets up the heart suit by playing the ace, queen and ruffing a heart. South can get rid of a diamond loser on the established heart, making 4.
This is the layout:
There are various considerations in the play, but the two most important are that South must resist taking the first club or the first heart. South must let West win the first trick in these suits with his kings.