Source: What can go wrong? By Eddie Kantar
The matchpoint duplicate players, have a high priority on not only making the contract, but scoring overtricks as well. In fact, it is almost de rigueur to risk your contract for the almighty overtrick(s) if the odds favor taking the chance.
On the other side of the fence is the play at:
- 1. Rubber (or money) bridge,
- 2. Any IMP -scored event,
- 3. Any doubled or redoubled contract,
- 4. Any superior contract reached playing matchpoints that the field is unlikely to reach.
Given any of these scenarios, overtricks are not the top priority — making the contract is first and foremost. This article presumes that your primary objective is making the contract. Here are two head-starting hints:
1. Ask yourself what can go wrong.
2. Assuming you spot an unhappy possibility, ask yourself what, if anything, you can do about it. If there is, do it!
Let’s start with this one:
After you open 1NT, partner gently raises you to game. West leads the 
3. Do you see anything here that we’ve been talking about?
You should. What can go wrong is this: Say you play low on the spade and East, that scoundrel, has the king, takes the trick, and shifts to a heart. Now, unless the hearts are blocked, if the player with the 
A has four or more hearts, then down you go. Could you have prevented this? Yes. Win the A (you still have a spade stopper) and drive out the A. Even if they find a heart shift, it’s too late. You have nine tricks: four clubs, three diamonds and two major-suit aces. Now try this one, and remember “the question.”
You decide to treat this 17-point hand as an 18-point hand and open 1. Partner responds 1
and raises your jump rebid of 2NT to 3NT. West, a broken record, leads the 3. See any trouble ahead?
You should. What if East wins the opening lead and shifts to a heart and West has the 
A? Suddenly a cascade of hearts will be heading your way. Can you do anything about it? Clearly you can’t if East has the A and West has the A. However, if you play the K at trick one you can at least save the day when East has the Q and West has the A.
Try this deal: 
Partner opens 1, you try 1, partner rebids 2 and you head for everyone’s favorite contract, 3NT.
West leads the 3 (what, no spade?) East plays the Q, followed by the K and then a third diamond to your ace as you pitch a spade from the dummy. West, if he can be trusted, has shown a five-card diamond suit. Can you see anything that can go wrong?
Well, if the club finesse loses (what else is new?) and a low spade comes back, you are not exactly a happy camper. Assuming this happens, your thinking should be: If West has the A, I can’t make this contract, but I don’t want to blow this contract if East has the A, so rise with the king. If it loses and West takes two more diamonds, big deal. You go down three instead of two if West has the A and East the Q. But you make the contract if East has the A.
Before leaving this deal, say you take the club finesse at trick four and it works! When you lead a second club to dummy’s queen, East discards a heart. Now what? You can’t set up clubs for five tricks because it means giving the lead up to West who has the setting tricks in diamonds. Recount your tricks: You have three clubs, four hearts and a diamond. You need one spade trick. Lead a spade to the king because you can’t make the contract if West has the A.