Bidding : 1C (S) - DBL (W) - Pass (N) - 2H (E) - Pass (S) - 4H (W)

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

Declarer (E) can count 6 possible losers in his hand : 2 in the trump suit and 4 in Clubs.
He can discard one Club loser on Dummy's Spades and ruff one or 2 in Dummy depending the enemy trump split. If South holds the trump Ace (which is likely as he opened and North passed throughout) he can, with careful play, limit the trump losers to one.

Declarer Play
Indirect finessing twice   -   discarding losers on High cards and by ruffing
South wins the opening lead, then, seeing Dummy is now void in Clubs, switches to his singleton Spade. Declarer wins with the Ace, and at trick 3 leads a small Heart, South plays low and Dummy wins the trick with the Queen.
At trick 4 Dummy leads a small Diamond to Declarer's King, who after winning the trick leads a second small trump on which South now plays the trump Ace winning the trick.
South must now be very careful, leading another Club or a Diamond will present Declarer with an extra trick. He therefore (at trick 6) safely "exits" by leading his last remaining Heart. Dummy wins the trick, the plays three rounds of Spades (K, Q and 10) on which Declarer discards a Club and ruffs on the third round.

At trick 10 Declarer leads his Club 10. If South is fool enough to cover it with his Ace, Declarer's Queen will provide an extra winner. South therefore plays low and Dummy ruffs with his last remaining trump. In the end Declarer concedes one more Club trick, making his contract, 10 tricks in total.

(At trick 10 Declarer could have played a low Diamond for a finesse against South's Queen. But if the finesse had failed (North having the Q instead) he would have lost 4 tricks in total, losing his contract. With his Club lead he ensured 100% success.)

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

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

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

Declarer (N) can count 5 possible losers : 2 in Hearts, 1 in Diamonds and 2 in Clubs.
He can discard the Diamond loser in his hand by playing 2 rounds of Spades before drawing trumps. For the rest he must hope that at least one of the suits (Hearts or Clubs) break favourably.

Declarer Play
Discarding a loser before drawing trumps   -   finessing against a 10
Declarer wins the opening lead with the Ace, then immediately leads his singleton Spade which is won by Dummy with the Ace. At trick 3 Dummy leads the Spade King on which Declarer discards his losing Diamond.
Declarer places East (who opened the bidding) with the Ace of trumps at least. Hoping that West perhaps may hold the Queen, he leads the trump 10 from Dummy for a direct finesse against the Queen. West plays low, so does Declarer but unfortunately East wins with the Queen. East, at trick 5, leads the Queen of Diamonds, ruffed by Declarer.

Declarer now leads his trump King, captured by East's Ace, who at trick 7 leads his singleton Club Queen. Dummy wins the trick, and then draws to last remaining enemy trump with his 8. At trick 9 Dummy plays the Club Ace. East shows out, which places West with the Club 10. Dummy now plays a small Club, when South plays low Declarer plays the Club 9 which wins. The remaining tricks are now all won in Declarer's hand (Club Jack plus the last trumps), making a total of 11 tricks (vulnerable).

Score = 5 x 30 trick pts + 500 bonus pts = 650 pts total

Bidding : 1H (S) - 1S (W) - 2H (N) - 2S (E) - 3H (S) - 4S (W)

Opening Lead : Ace of Hearts (N) = top honour of Partner's suit (avoid leading away from an Ace in a trump contract)

Declarer (W) counts 5 possible losers : one in Hearts, 2 in Diamonds and 2 in Clubs. He must reduce it by finessing successfully in at least one of the suits.

Declarer Play
Direct and Indirect finesses
East wins the first trick, then leads a small Heart, South plays his Queen which is ruffed by Declarer. Declarer now leads two rounds of trumps ending up in Dummy.
At trick 5 Dummy leads the Jack of Diamonds, South wins the trick with the Ace and exits with the Jack of Hearts, ruffed once again by Declarer. Declarer now (trick 7) leads a small Club to Dummy's King which is captured by South's Ace, who once more leads a Heart. Declarer ruffs again, then leads a small Club at trick 9. When North plays low, Dummy plays to Club 10 which wins.
At trick 10 Dummy leads the 10 of Diamonds, South plays low as there is nothing to be gained by sacrificing his Queen. Declarer plays low too and Dummy's 10 wins the trick. The remaining tricks are now won by Declarer (Diamond King plus the last remaining trumps), making 10 tricks in total.

Score = 4 x 30 trick pts + 500 bonus pts = 620 pts total

Bidding : 1H (E) - 1S (S) - Pass (W) - 2S (N) - Pass (E) - Pass (S) - Pass (W)

Opening Lead : 2 of Hearts (W) = singleton in Partner's suit

Declarer (S) counts 5 possible losers : Aces of Spades and Hearts, plus perhaps 3 losers in Diamonds.

Declarer Play
Ruffing high to prevent an over ruff
East wins the opening lead with his Ace and returns a small Heart. Declarer plays the King, which, unpleasant surprise, is ruffed by West with the Spade 5.
West noticing Dummy's Club Ace, leads a small Diamond at trick 3, hoping to bring the lead back to his Partner. East indeed wins the trick with his Diamond King (showing Partner he has the Diamond Ace as well). At trick 4 East leads a third Heart. Declarer is now out of Hearts too, but he must ruff high with his Spade 10 (or better) to prevent West over ruffing with the 9.

Declarer wins the trick and (trick 5) leads a small trump to Dummy's Queen, captured by East with the Ace. East once more leads a 4th Heart, ruffed again high by Declarer who wins the trick. Declarer now (trick 7) leads his King of Spades which draws the enemy's last remaining trumps. he then leads a small Diamond and , when South plays low, plays Dummy's 9 won by East Diamond Ace. The remaining cards by Declarer and Dummy (A K Q of Clubs, Q of Diamonds plus one trump) win the remaining tricks of the game, 8 trick in total.

Score = 2 x 30 trick pts + 50 bonus pts = 110 pts total