Handle one suit to help in another
Kin Hubbard, the creator of the cartoon Abe Martin of Brown County, said, "Honesty pays, but it doesn't seem to pay enough to suit some people."
Playing suit combinations correctly pays at the bridge table. An expert enjoys an advantage because he knows so many of them, but even then, care might be needed. What should South have done in his four-spade contract after ruffing the third round of clubs?
Remember that you do not pre-empt against a pre-empt. Jump overcalls are strong. South has three top losers: two clubs and one spade. So he must find East with both of the red-suit kings. However, he probably needs to take three finesses: one in hearts and two in diamonds. This requires either lots of dummy entries or being able to run a card from the dummy that can win the trick assuming the finesse is successful.