Defending isn't easy. Nothing feels worse as a defender than when declarer starts to claim and you look down at an ace that won't take a trick. That is a visceral feeling, but players don't notice as much when they take their ace too early and give up an extra trick as a result. This second situation is much more common. So when is it right to take an ace? A good rule is to avoid playing your ace "on air" (not capturing an honor), but an even better rule is to "think".
Test yourself on these deals.
Let's start with a lead problem.
You are West.
A8653 
Q5 
J1098 
AQ
The auction is:
| West | North | East | South |
|---|---|---|---|
| 1 |
Dbl | 2 |
3 |
| All Pass |
What is your lead?
A
Low Spade
5
J
A
This time you are East. What should you play in the following situation (assuming standard signals)?
| West | North | East | South |
|---|---|---|---|
| 1NT | |||
| Pass | 2 |
Pass | 2 |
| All Pass |
Partner leads the J. Dummy plays low.
| Vul:None Dlr: S |
DUMMY
|
|
|
YOU
|
||
What spade do you play?
A
9
5
The joker that I keep in my pocket for emergencies
You are East, again. Standard signals. What's your play at trick one?
The auction:
| West | North | East | South |
|---|---|---|---|
| 1 |
|||
| Pass | 3 |
All Pass |
Partner leads the Q.
| Vul:E-W Dlr: S |
DUMMY
|
|
|
(YOU)
|
||
A
10
8
6
You are East. The contract is 3NT on the auction below.
| West | North | East | South |
|---|---|---|---|
| 1NT | |||
| Pass | 3NT | All pass |
Partner leads the J.
| Vul:None Dlr: S |
DUMMY
|
|
|
YOU
|
||
You play the 7 (standard). Declarer plays the 3. Partner plays the 8 and you play the Q, declarer taking the A. Now declarer leads a club to dummy's K, partner playing the 3. And you?
Take the ace and play a diamond
Take the ace and play a spade
Take the ace and play a heart
Duck smoothly
Think a long time and then duck
You are West. The contract is 4 on the auction below.
| West | North | East | South |
|---|---|---|---|
| 2 |
|||
| Pass | 4 |
All Pass |
You lead the J.
You take in dummy--a bit of an overbid. Maybe South is a famously conservative preemptor.
| Vul:Both Dlr: S |
DUMMY
|
|
|
YOU
|
||
Declarer wins A in dummy (partner playing the K which should promise the Q). Declarer now plays a low heart to the ace, partner playing the 5. Declarer now leads the 8. What do you do?
A and play a spade
A and play a club
A and continue diamonds
A and play a heart
Some low diamond
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