Here's a lead problem from the 2009 Trials you are sure to get wrong

 (maybe that will help you get it right?):

A 7 6 5 3
9
9 8 3 2
10 4 3
LHO, who is trailing late in the match, opens 2, strong. This is the auction:

LHO	Partner	RHO	You
2	Pass	2	Pass
3	Pass	3	Pass
6	Pass	7	Pass
Pass	Double	Redouble	All Pass

What is your choice? Maybe partner's double is Lightner, asking for dummy's first suit. Could he be void in diamonds? But, declarer redoubled. No doubt, he is ready for a diamond lead. Or, maybe he is just redoubling because he trails in the match. Maybe you should try to cash your A first?  This was the full deal:

Vul: N-S Dir: West	-- A J 3 A K Q J 7 6 4 Q J 2
A 7 6 5 3 9 9 8 3 2 10 4 3		J 10 9 4 2 7 2 10 5 A K 9 5
	K Q 8 K Q 10 8 6 5 4 -- 8 7 6

This deal knocked out the #3-seeded JOHN DIAMOND team. Note the team name. Diamonds was the suit led by Geoff Hampson. Declarer (Melih Ozdil) soon claimed all 13 tricks for a whopping score of 2940!

Of course, a club lead would have led to down two and a score of 1000 for E-W. How could West possibly know?  (Maybe if he were playing for the "CLUB" team.? Maybe East thought the double was for dummy's first-bid "suit"--clubs. When the suit is artificial, this usually isn't the way a Lightner double is used.

In any event, with or without the double, I don't see how West could ever figure out to lead a club. At the other table in the match, East-West "sacrificed" in 6 doubled down 1,100. With a club lead against 7XX, DIAMOND would have won 19 IMPs. With the diamond lead, they lost 18 IMPs. A 37-IMP swing on opening lead!!!!

(For another huge swing on lead, see this article from 2006)