Unless North is playing a very deep game by holding back with the spade king, this is the best way to increase your chances.
Declarer must set up his diamond suit, so he should take a precaution against a 5-2 spade division. By ducking the opening lead, declarer prevents South from bringing in his long spade suit unless he has both diamond honors. Suppose North returns a spade, assuring you of two tricks in the suit; when you drive out one of the diamond honors, North either has no spade to return or the suit will originally have been divided 4-3. In either case you make your contract.
It is not likely that North, having won the first trick, will shift. Should he do so, you can always finesse for the king of spades yourself.
South's actual hand is: spades K 9 8 6 2, hearts 3 2, diamonds K 7 6, clubs Q 9 5. Notice that if East wins the first trick with the spade queen, North will take care to win the first round of diamonds and return a spade, and East will still have to let South into the lead with the diamond king.
AS FOR THOSE PUZZLES...
On the Lenz hand, South discards a diamond on the ace of clubs, and North leads the club king.
1) If East trumps, South overruffs, cashes the spade ace, ruffs out West's spade king, and North leads trumps to pick up East's queen.
2) If East discards a spade, South ruffs, trumps out West's spade king, leads a heart from North for a winning finesse and cashes his good spades. North is put in with a diamond to lead a club for South to ruff. A second diamond puts North in and East's trumps are couped.
3) If East discards a diamond, South discards a spade. A heart is led for a finesse, dummy is reentered with a top diamond for a second heart finesse, and South runs all his trumps. West is squeezed in three suits.
On the Whitfield Six, South leads the diamond king and North plays the diamond jack! A spade lead is ruffed with the heart 7, and North leads the heart 8. East throws the club 8, South the club 10. West cannot safely discard other than the spade queen. North leads the club ace. If East discards the spade jack, South discards the diamond 9 and wins the last two tricks with his remaining diamond and spade. If East discards the diamond 8, South discards his spade leaving him with two good diamonds.