Bidding : 1C (N) - 1S (S) - 2S (N) - 4S (S) - Pass (N)

Opening Lead : King of Hearts (W) = top of a solid sequence

Declarer (S) counts 4 possible losers in the combined hands : two losers in Hearts (once his Ace has gone), one loser in Diamonds and one in the trump suit if the enemy Spades are divided 4-0.
He plans to discard a small Diamond on one of Declarer's Club winners

Declarer Play
Overtaking an Honour with an Honour to transfer the lead   -   Discarding a loser
Declarer wins the first trick with the Ace of Hearts in his hand. He then leads a small Spade to Dummy's Ace. Both Opponents follow suit, therefore the trumps will break 3-1 or 2-2. Declarer wins the next two rounds of trumps in his hands to remove all Opponents trumps.
At trick 4 he plays Dummy's Club Ace, King and then the Jack which he overtakes in his hand by the Queen. Declarer now (trick 7) leads to Club 10 from his hand on which a losing Heart is discarded in Dummy.
This reduces his losers from four to only two and enables him to make one overtrick.

Score = 5 x 30 trick pts + 300 bonus pts = 450 pts total

Bidding : 1D (E) - 1S (W) - 4S (E) - Pass (W)

Opening Lead : King of Clubs (N) = King from A K x x

Declarer (W) counts at least 3 potential losers : one in Hearts, one in Diamonds and one in Clubs. To avoid more Club losers Declarer must get rid of some of the Clubs in his own hand or ruff them in Dummy.

Declarer Play
Playing through Dummy's strength   -   Forcing out Opponent's Ace to establish winners
North wins the first trick with the King of Clubs. Seeing the singleton Club in Dummy, North decides to switch the lead for trick 2 to Hearts.
This is a safe and good defensive lead (playing "through Dummy's strength"), rather than leading another Club (which would be ruffed by Dummy) or cashing his Diamond Ace (which would make Declarer's life only easier).

After winning trick 2 with Dummy's Heart Ace, Declarer removes the Opponents trumps with three rounds of Spades. He then leads the Jack of Diamonds, forcing out North's Ace (trick 6).
North leads another Heart (trick 7), won by Dummy with the King. Dummy's Diamond winners are then played out on which Declarer can discard one losing Heart and two small Clubs.
In trick 12 Dummy's small Heart is ruffed in Declarer's hand, which leaves Dummy's trump Queen as a winner for the last trick. Declarer makes 11 tricks in all.

Score = 5 x 30 trick pts + 300 bonus pts = 450 pts total

Bidding : 1H (N) - 1NT (S) - 3H (N) - 4H (S) - Pass (N)

Opening Lead : Queen of Spades (E) = top of a solid sequence

Declarer (N) counts at least 4 possible losers : at least 1 trick in the trump suit (perhaps two if the Opponents trumps break 4-1 or worse), 1 in Diamonds, 1 in Clubs and also 1 in Spades if Dummy is out of trumps.

Declarer Play
Ruffing in Dummy before drawing trumps   -   Finesse of K Q against the Ace
This is a typical case where North should not draw trumps first.
Declarer wins the first trick with the Spade Ace. He then leads the Spades King in trick 2, followed by a small Spade in trick 3 which is ruffed in Dummy. Now one potential loser has been avoided and it is safe to draw the Opponents trumps.

After two rounds of trumps Declarer switches to Diamonds (trick 6), leading a small card up to Dummy's King in the hope that East holds the Ace. Unfortunately West holds the Diamond Ace instead and captures Dummy's King. However the contract is secure with the Diamond Queen, Club King (or Queen) and the remaining trumps minus one (lost to North's Queen) providing 10 tricks in all.

Score = 4 x 30 trick pts + 300 bonus pts = 420 pts total

Bidding : 1C (W) - 1H (E) - 3NT (W) - 4H (E) - Pass (W)

Opening Lead : King of Spades (S) = top of a solid sequence

Declarer (E) counts 4 possible losers : the Ace of trumps, the Ace of Diamonds and 2 Spade tricks.
On any other opening lead Declarer would been able to draw the Opponents trumps first (as usual).
However being forced to play the Ace of Spades at the first trick immediately exposes the two Spade losers.

Declarer Play
Discarding losers before drawing trumps   -   Forcing out Opponent's Ace to establish winners
Declarer wins the opening lead in Dummy with the Spade Ace.
If Declarer plays a trump at trick 2, the Opponents will immediately gain the lead with the trump Ace and then cash the Spade Queen and Jack. Together with their Ace of Diamonds they will make 4 tricks and defeat the contract.

Therefore (at trick 2, 3 and 4) Declarer plays the three Club winners from Dummy (A, K and Q) on which he discards from his own hand his only Club and the two Spade losers.
This reduces his losers from four to only two. Declarer can now trick 5 proceed with drawing all Opponents trumps.   After that Declarer forces out the Diamond Ace to establish two more winners in Diamonds, making 11 tricks in total.

Score = 5 x 30 trick pts + 300 bonus pts = 450 pts total