For a warmup, here's a bidding and play problem faced by England's Phillip King (coauthor of The Kings' Tales and many other fabulously entertaining bridge books).
Phillip was in fourth seat at all vul and held
His LHO opened 3H, and there were two passes to him. What would you bid in this situation?
Phil pulled out a brave 3NT! Here's the whole hand:
South was leery about leading away from his hearts, so he started with the ♠8, won by declarer's stiff ace. The ace and king of clubs were cashed, and King was pleased with the drop of the ♣QT giving him two entries to dummy in the club suit. He led to the ♣J (South pitching the ♠6) and tried to run the ♦9. North covered with the ♦10 and King won with the ♦J. He played his last club up to the dummy, South pitching a heart and North a spade. Then came the ♦4 to the ♦8 (both defenders following) and he stopped to take in the distributional information.
If diamonds were 3-3, he could cash the ace and claim ten tricks - five diamonds, four clubs, and a spade. Could that be the case? He decided not. South had led a spade and pitched a spade, so he had two there. He'd followed to two clubs and two diamonds. With the opening 3♥ call almost always showing 7, all thirteen of South's cards were known! So there wouldn't be a friendly diamond split. Since he knew all thirteen cards in the South hand, he could work out the North hand as well. These are the remaining cards as seen in declarer's mind's eye:
Taking the only chance he could see, he led a low heart from his hand! South (who, remember, had AQJ9762) couldn't work out the position (the ♥A from him allows him to claim the rest of the tricks!) and played the ♥J. North had to win the trick and was endplayed into giving declarer two spade tricks or two diamond tricks. Declarer just lost two spades and two hearts for a scary +600.