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

Opening Lead : Jack of Diamonds (E) = top of a solid sequence

Declarer (N) counts 6 possible losers. There is a very small chance of one loser in the trump suit (Spades) if the enemy trumps are divided 1 - 4, with the Spade Jack in the 4-card suit.

There is also a possible Heart loser if the opponents' hearts break 4-2 or worse. There are four certain losers, 2 in Diamonds and 2 in Clubs (after that Declarer can trump further enemy leads in these suits). This adds up to a total of 6 possible losers, one too many for making the contract.

Declarer Play
Drawing the enemy trumps first   -   Establishing a winner by ruffing   -   Discarding a loser
The Opponents ("enemy") win the first 2 tricks (A and K) in Diamonds. West notices Declarer dropping the Queen on the second trick and therefore switches to Clubs, with East winning first the Queen, then his Ace, but refuses a third round of Clubs as this would promote Dummy's Jack (or 10) to a winner (Declarer would also trump West's King).
At trick 5 East therefore exits (= safely gives the lead away) with the Jack of Hearts, won by Declarer with the Ace.
Declarer, on lead at last, now first draws three rounds of trumps, which removes all Opponents' trumps (breaking 3-2).
At trick 9 Declarer leads a small Heart to Dummy's King.
Dummy then leads the Jack of Clubs (trick 10) which forces out West's King, ruffed (trumped) by Declarer. Declarer (at trick 11) now leads another small Heart to Dummy's Queen. Dummy after winning that trick leads his Club 10 winner on which Declarer discards his small Heart loser. The last trick is won by Declarer remaining trump.
The Opponents' Hearts do break 4-2, but as Declarer showed, there are more ways to skin a cat. He is rewarded with his effort for making 9 trick in total.

Score = 3 x 30 trick pts + 50 bonus pts = 140 pts total

Bidding : 1S (E) - 3S (W) 4S (W) - Pass (E)

Opening Lead : King of Clubs (S) = K from A K J 10

Declarer (E) counts 4 possible losers, one in Spades (Q) if the Opponents' trumps break 3-1 or worse, one in Diamonds (Q) and two in Clubs (A K).

Declarer Play
Drawing trumps first - 8 ever 9 never - Discarding a loser
South plays and wins the King and Ace of Clubs and, seeing Dummy is now void in the suit, switches to a small Diamond at trick 3, won by Declarer with the Ace.
With 9 trumps in the combined hands excluding the Queen (and Opponents having 4 only) the best approach is to play first the Ace and then the King for the drop of the Queen (see 8 ever, 9 never). Declarer does just that and drops the trump Queen on the second round.
At trick 6, 7 and 8 Declarer cashes his A, K and J of Hearts. At trick 9 he crosses over with a small Diamond to Dummy's King. Dummy now leads his Heart Queen winner on which Declarer discards his small Diamond loser. The remaining three tricks are all won by Declarer's remaining trumps, making a total of 11 tricks.

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

Bidding : 1S (S) - 3S (N) - 4S (S) - 6S (N) - Pass (S)

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

Declarer (S) counts 3 possible losers, two Diamond losers in his own hand and a possible Spade loser (J) if the Opponents trumps break 4-0. But if the four enemy trumps are divided 4-0 a trick is only lost if East holds J x x x x.

One of Declarer's Diamond losers can be discarded on one of Dummy's Club winners. The other Diamond loser can be discarded on Dummy's 4th Heart if the Opponents' Hearts break 3-3.

Declarer Play
Discarding losers   -   Establishing an extra trick when Opponents' cards are divided 3-3
Declarer wins the opening lead with the Diamond Ace, and then proceeds to draw all Opponents trumps in 3 rounds (they break 3-1).
At trick 5 Dummy leads a small Club to Declarer's Ace which wins and a small Club is returned to Dummy's Club King. At trick 7 Dummy leads and wins the Club Queen on which Declarer discards a losing Diamond. Dummy now leads a small Heart to Declarer's Ace. The next trick (trick 9) Declarer returns a small Heart to Dummy's King. A third round of Hearts is won by Dummy's Queen and reveals that the Opponents' Hearts were divided 3-3. Dummy then leads his last remaining Heart which is now a winner on which Declarer discards his second Diamond loser.
The remaining tricks are all won by Declarer's remaining trumps, making all 13 tricks in total.

Score = 7 x 30 trick pts + 800 bonus pts = 1010 pts total

Bidding : 1H (W) - 2H (E) - 4H (W) - Pass (E)

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

Declarer (W) counts 4 possible losers. Two in Hearts if the enemy trumps break Q J x x , one loser in Diamonds (Q) and one loser in Clubs (A).
The Club loser and at least one trump loser are unavoidable, but the Diamond loser in Dummy can be discarded on one of Declarer's winners in Spades.

Declarer Play
Drawing the Opponents' losing trumps only   -   Discarding a loser   -   Eliminating a loser by ruffing
Declarer ruffs the second Club lead in his own hand, then draws two rounds of trumps with his Ace and King of Hearts. The Opponents now have one high trump winner left (the Jack) but Declarer should not waste his own and Dummy's trumps on that.
Instead Declarer now (trick 5) leads a small Spade to Dummy's King, which is followed by a small Spade from Dummy to Declarer's Ace. South ruffs the next Spade lead (Q), but Declarer's remaining Spade winner (J) can now be used to discard a losing Diamond in Dummy and then ruff Declarer's losing Diamond with Dummy's last remaining trump.

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