Source: http://www.mrbridge.co.uk/
You are South as declarer playing teams or rubber bridge. In each case, what is your play strategy?
1. You are declarer in 3NT and West leads the 
7. East plays the J. How do you plan the play?
3. You are declarer in 3NT. West leads the 4 and East plays the K. How do play?
2. You are declarer in 4 and West leads the 
Q. How do you plan the play?
4. You are declarer in 4
after East has bid spades and West has not raised. West leads the 4; East plays the K followed by the A; West follows upwards. East then plays a third round. How do you plan the play?
Answers to David Huggett’s Play Quiz
1) You are declarer in 3NT and West leads the 7. East plays the J. How do you plan the play?
The lead 
has done you no harm at all and a quick tally of the top tricks comes to eight. While, clearly, the club suit will furnish extra tricks, you really do not want to lose the lead to East. Why is that?
Well in a worst case scenario, he might win the fourth round of clubs and lead a heart through your king; then, if the ace of that suit sits over your king, you might end up losing at least four heart tricks and a club. As you need only four club tricks to guarantee your contract, you should take out insurance by playing a low club to the king followed by a club to the nine, finessing against the jack. Whatever happens, you keep East out of the picture. 
2) You are declarer in 4 and West leads the Q. How do you plan the play?
Assuming no spade loser, you have nine tricks on top. Although the tenth could come from a successful diamond finesse, a Leiter plan is to try for a heart ruff in dummy. So, win the opening lead and play a low heart. They can win and play a trump; you can win that cheaply and play a second heart; even if they play a further round of trumps, you will still have one in dummy to take care of your third heart loser. Note that you must not play even one round of trumps. If you do, you might find that you have no trumps left in dummy for the intended heart ruff. 
3. You are declarer in 3NT. West leads the 4 and East plays the K. How do play?
It looks as though the spades are divid-ing 4-4, a comfort because you have to play on clubs for your extra tricks, which means losing the lead. After you play the ace of clubs followed by a low one, you appear to be on a guess if West follows low: if West has the king, you want to play dummy’s queen; if West has the jack, you want to play the ten. However, you have also to consider the times when clubs break 4-2. A doubleton king with East will do you no good even if you guess right: you will still have two club losers. By con-trast, a doubleton jack with East will be fine — but only if you play the queen from dummy — so that is what you should do.
4. You are declarer in 4 after East has bid spades and West has not raised. West leads the 4; East plays the K followed by the A; West follows upwards. East then plays a third round. How do you plan the play?
The contract is a poor one and you will need some luck to succeed. Thinking about it, you can see how futile it would be to ruff the third spade in dummy for then you will hove at least two guaran-teed trump losers. (Even if East started with just the ace and queen of trumps, he might be in a position to play a fourth round of spades to promote his partner’s ten.) So take the ruff in hand and enter dummy with a diamond to lead a trump. If East were to play low, you would seem to be on a guess whether to play the jack, hoping for the A-Q onside or the eight, hoping for the Q-10 onside. It would not really be a guess because, if East held A-Q-x, he might beat you by rising with the ace and playing a fourth spade to promote West’s ten of hearts. You would thus play the eight. As the cards lie, that decision does not arise. East goes up with the ace and plays another spade; you must ruff with the eight and when it wins, you re-enter dummy to play a further trump to finesse against the queen. Assuming a 3-6 spade break and competent defence, you will make the contract only if East started with Q-10-x, Q-10 or A-Q-10 in trumps.