Learn to trust your partner.
North-South vulnerable.  
South deals.
                              NORTH
                              S: K J 8 2            
                              H: 9 5 4       
                              D: J 10 8 7 6  
                              C: 7       
            WEST                             EAST
            S: 10 9                          S: Q 7 6 5 3    
            H: Q 8 6 3                       H: 10 7 2     
            D: Q 5                           D: K 4               
            C: Q 10 9 8 3                    C: K 5 4       
                              SOUTH                         
                              S: A 4   
                              H: A K J      
                              D: A 9 3 2   
                              C: A J 6 2  
	The Bidding:
                  SOUTH    WEST    NORTH    EAST                  
                   1S      Pass     1D      Pass
                   2NT     Pass     3NT     Pass
                   Pass    Pass
	Opening Lead: 10C
     Cover the South and West hands and consider your play from
the East hand after your partner leads the ten of clubs against
three no trump.
     Your first question should be "What does the lead of the ten
tell me?".  Your partner is either leading the top of nothing or
the top of an interior sequence.  
     Your second question should be "What could partner have in
high card strength?".  South has shown a twenty count (give or
take a point), you have eight high card points and North, the
dummy, has put a king and two jacks on the table for a total of
five high card points.  This leaves a possibility of six, seven,
or eight points in partners hand.  
     The next question is "Why did partner lead a club,
declarer's first bid suit?".  These type of auctions tend to
scream for the lead of a major suit.  Partner is a good player
and yet did not lead a major.  There must be a reason.  Either
partner has unprotected honors in the major suits and does not
want to give anything away, or clubs is the suit that he wants to
attack.
     Now for the key question.  "What card do I play to this
trick?"  If partner has led the top card of a sequence then
playing the king will give up a trick.  Declarer cannot finesse
again because there are no more clubs in the dummy.  On the other
hand, if partner has led the top of an interior sequence, you
must play the king to support the attack on the club suit.  If
that is wrong, you have given up one trick in defense.  If it is
right to play the king and you don't, you have probably given up
the entire hand.
     So, what is the answer?  Trust your partner and play the
king.  It is much more likely that partner has the holding shown
above and South will have a very difficult decision to make after
your king hits the table.  Ducking twice is right and many
declarer's will find this play but those who elect to win the ace
will have to play the diamonds right to avoid a club continuation
through the jack.
     Would it be easier if partner led the three of clubs instead
of the ten?  It may seem so on the surface, but the ten caters to
many other distributions that are possible on this hand.  For
instance, what if declarer held ace-six-two opposite jack-seven
in the dummy?  The ten has now neutralized the jack.  
     Partnership defense is difficult at best.  Trust and
confidence are built over time by making thoughtful plays.  Every
card that you play may not be correct, but if you have asked
yourself the proper questions, you will more than likely come to
a supportable decision.  And try to remember, a card must be
played on the same day that it is dealt.
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