Famous English top player and bridge author Terence Reese (1913-1996) once wrote about kibitzers (spectators at a bridge match) that if they saw top class dummy play, they looked upon declarer as some kind of wizard. Especially kibitzers who are inexperienced players themselves, seem to think top players know all about the distribution of suits and honour cards as soon as the bidding is over.

Of course good players are not wizards. They gather information and during the play they build with it an increasingly accurate picture of the deal. They are just better (and faster) in doing so than lesser players. All the more since during this building of their picture they include the strategy and discarding of the defenders.
Lesser players usually miss such 'soft' information, they cannot go beyond the collecting of 'hard' information, like: 'West did not follow suit in the second round of spades, so East has four' or: 'since he opened the bidding, he must have the ♦A'.
Once the picture is complete, it is only a matter of technique and there it is... another bit of magic.

In the deal below we follow declarer's line of thinking while he - seemingly - produces a bit of magic. By the way, he is helped (!) by the fact that his opponents are first class as well.

W/EW		♠	8 5 3 2
		♥	Q 7 4 3
		♦	J 6
		♣	K 8 6
		♠	10 7 6
		♥	A K J 10 5
		♦	K 2
		♣	A J 5

¹ North does not bid hearts first, which looks more normal, since he is anticipating on bidding once more. If EW would bid again (say 2♦) and South would pass, North plans to bid 2♥. This sequence therefore does not promise 5-4 in this specific case.
If North would start off 'normally' by bidding 1♥, he is unable to bid spades later without the risk of getting to the three level (naturally he is too weak for a 2♦ cuebid).
² South's sequence 'doubling first and bidding his own suit (or no trumps) later' would promise at least 18 points directly behind the opening bidder. Now, fourth in hand, some (14)15 points suffice. The reason is that any bid fourth in hand can be weaker than the same bid in the second hand (fourth in hand we can for instance sometimes overcall on a mere six points and a shabby five card suit).

The contract is too high (especially because of the duplication in diamonds; perhaps South should have opted for a 1♥ overcall instead of the double, in view of the unfavourable position of his ♦K before the 1♦-opener). But then again, had South been in 2♥ his dummy play would not have needed to be that good!

West leads the ♠A and on seeing East's ♠Q (showing the ♠J) continues with the ♠K and ♠4, to East's ♠J. Dummy's fourth spade is now good. After some thought East switches to the ♥2.
South has lost three tricks and a certain diamond loser (he can discard one diamond on the good spade), so he has to avoid a club loser. How should he proceed?

First the 'hard' information: since East has shown up with the ♠QJ, he cannot hold the ♦A (he passed West's 1♦ opener). He can hold the ♣Q though - just. Average players do not get any further. They draw trumps, throw a diamond on the good spade and finesse the ♣Q over East.

A 'wizard' would not even consider that finesse, it is bound to fail. Why? Because East did not switch to a diamond!
Let us explain that. Firstly: East did not switch to a trump in order to prevent diamond ruffs in dummy: he can easily see that South, holding at least eight cards in the major suits and the ♣A, has at most one diamond to ruff and there is no way EW can prevent that.
Why then did East play a trump and not a diamond?

Suppose East has the ♣Q (that is what these average players hope for). South would know five points in East's hand then. More is not possible, so West would hold the ♦AQ then. East knows West does not hold the ♦AK: West would have led or switched to that suit instead of making good North's spade. So in East's opinion West would then have the ♦KQ or, more likely, the ♦AQ. Meaning East certainly would have switched to a diamond.

But he did not. This can only mean that he can see that such a switch might cost a trick. Therefore East has the ♦Q! As a consequence West has the ♣Q.
So the club finesse is off.

Should South then top the ♣AK, hoping to bring down West's ♣Q?
The wizard continues his logical way of thinking: since East turned out to have five points, he cannot have four diamonds: he would have supported by bidding 2♦ in second instance (after North's 1♠ bid). On the other hand, West cannot have seven diamonds, he would have bid 2♦ over South's double. This leaves one possible diamond distribution: West has six (with the ♦A) and East three (with the ♦Q).

Thanks to all this 'soft' information South now knows the distribution in diamonds and spades and the position of the ♣Q. Time for action: the declarer wins with the ♥A (West the ♥6) and plays a heart to the ♥Q.
West discards a diamond! The picture is complete: West has 3-1-6-3, the ♣V will not come down:

W/EW		♠	8 5 3 2
		♥	Q 7 4 3
		♦	J 6
		♣	K 8 6
♠	A K 4			♠	Q J 9
♥	6			♥	9 8 2
♦	A 9 7 5 4 3			♦	Q 10 8
♣	Q 10 7			♣	9 4 3 2
		♠	10 7 6
		♥	A K J 10 5
		♦	K 2
		♣	A J 5

But that does not pose a problem. There is a technical solution to deal with this distribution. Declarer plays off all trumps, closely watching West's discards. Then he crosses to the ♣K. Suppose West has discarded diamonds all the way on the trumps (meaning four), which is logical. The situation now is:

W/EW		♠	8
		♥	-
		♦	J 6
		♣	8
♠	-			♠	-
♥	-			♥	-
♦	A 9			♦	Q 10
♣	Q 10			♣	9 4
		♠	-
		♥	-
		♦	K 2
		♣	A J

Declarer now cashes dummy's good ♠8, discarding the ♦2 in his hand (East is unimportant).
West is powerless.
- If he discards the ♦9, a diamond from the dummy is played to his ♦A and he has to play into the club tenace.
- If he throws a club, South cashes two club tricks.

It does not help West to discard differently: South knows West's distribution and therefore knows when West blanks his ♦A or ♣Q.

Wizardry? No, just a matter of gathering hard and soft information and having a thorough mastery of playing techniques! (This one is known as a 'strip squeeze'.)