This is from Imagination and Technique in Bridge, by Bourke and Hoffman. Righty opened the bidding 1H and you are playing 6S. The opening lead is a small heart.
What is the best play for contract?
Placing the cards, Righty will no doubt have the KQ of clubs. If everyone comes down to three clubs at the end, you can lead a club to the jack, endplaying Righty. (Or, if you are in dummy, lead the jack and let Righty win.)
That means a squeeze-trim-endplay against Righty. The loser count is two (counting one club as a winner). Righty can be endplayed in clubs and cannot afford to discard down to KQ of clubs, as long as you retain a control in the heart suit. You have to hope that that Righty does not have 4 diamonds, but Righty probably does not. So everything, almost, is in place.
The last free winner has to come from dummy, because you have to be in dummy to lead a heart for the trimming operation. That means you first run all of your spades except one, then go to the board and cash diamonds. The situation before you lead your last diamond, assuming that Righty threw some diamonds on the spades:
If Righty throws a club, you can just lead clubs and only lose two tricks. If Righty throws a heart, you ruff a round of hearts. Then lead a club to the jack, endplaying Righty.
Squeeze-Trim-Endplay: Trump as a Control