Source: ACBL 2007 Bulletins
Spot cards, as noted in this series, are important. I once played a 2
doubled contract and was faced with this trump layout in the ending:
East was on lead and he played 
J. I ruffed, but West ruffed too, and he earned a trick with the 3! I wish I had the entire deal to report, but it was too long ago. I only remember the ending. There is a message here, however. Trumps are important something no one will argue with. The bigger they are, the more potential they have to become tricks. Sometimes, however, even low trumps can become winners. Consider the following example (South deals, both vulnerable):
You are on lead against 4. After this unusual sequence. You ask what 4 showed and North explains that it has not been discussed. He does allow that South ought to have a very good suit for this sequence. You lead the 
A (A from A-K)
and East plays the 10.
What now?
It looks like East has a doubleton heart, but there is a tiny chance that he has a singleton. With nothing else looking hopeful, you continue with the K. East and South follow.
Where now? You lead the J, dummy plays the queen, and East ruffs with the 8. South overruffs with the queen and
leads the 10.
Any idea?
One thing is clear: South does not have any losers in the minor suits.
If you are going to set 4, it has to come from the trump suit. You could play low on the 10 hoping for East to have the king, but in all honesty, is it possible that he has it?
South opened and jumped to game. He may not be bidding the way you think he should, but you should still credit him
for the K Q J 10.
If he has them, is there a way to set 4? Actually, there is. If South has six spades, East has three. East has already shown up with the 8. If he has the 9, too, there is a way.
Play the A on South’s 10. Do not fall for South’s little deception.
On your ace, East follows with the 3. Given that there is only, one hope for the defense, you lead the 2 . Your partner, aware that you have a purpose in leading hearts, ruffs the fourth round with the 9, forcing out South’s king. Your 7 is the setting trick. Here is the entire layout: