Another area where ill-feeling abounds:

Law 74B: Etiquette

As a matter of courtesy, a player should refrain from … prolonging play unnecessarily (as in playing on despite being certain to take all the tricks) for the purpose of disconcerting an opponent.

In other words, do not play on when you have the rest of the tricks, especially if opponents appear to be struggling with discards.  Many declarers, particularly less experienced players, fear to claim in case defenders argue.  A more experienced player may be in a position to concede – in a friendly manner! 

Make your claim clearly, stating an exact line of play if necessary, e.g. "dummy is high" or "drawing your last trump, then cashing the diamonds".   Face your cards and allow opponents to examine the situation.

As a defender you may think the claim is flawed.  In that case you must call the TD (or his deputy in a club where the TD is also playing) for arbitration.

 You may not insist that declarer plays his cards in a specific order so that you make extra tricks – that is a decision for the TD.

You may not accept the concession of a trick that you cannot possibly win, e.g. declarer says "I shall play winners, make your trump whenever you like".  If you no longer have a trump you may not accept the trick.

If the claim is disputed you should normally call the Tournament Director; but if all four players agree play may continue till the situation is clarified.  We should encourage players to claim: remember to be nice if you think the claim is flawed.