Here is a hand from Wednesday. I was sitting East with 12 points. Opponents were silent. My partner opened one diamond in 2nd seat, one spade by me, two diamonds by partner, three clubs by me, three hearts by partner, three notrump by me, and three passes.
South led the seven of hearts. I played low from dummy and my jack won the trick. I counted my sure tricks: two hearts, five diamonds and two clubs. At trick two I started running the diamonds, hoping that I could set up an overtrick in clubs. That was too lazy.
I forgot to remember an obvious inference for South’s heart holding from trick one. I should have made a mental note that South had to have the king, queen, nine, and perhaps one more in hearts. When I observed South discard the nine of hearts on the last diamond, I must lead the ace of hearts and out a heart to set up my 10 of hearts for a 10th trick. All the opponents can get is one heart and two spades.
BTW, I recommend that West rebid one notrump at her second turn. The two diamond rebid implies six diamonds.