It is fine to employ whiz-bang bidding systems with loads of conventions. True, if you can remember all of the calls and use them at the right moments, your bidding will be more accurate. But sometimes a pretty method helps the defense more than the declaring side — as in this deal.
    Look only at the West hand. You know that South has 4-5-1-3 distribution with 11-15 high-card points and one ace. North's hand is unknown except that he selected six clubs as the final contract, given what South had described. What would you lead?
    South used the Flannery convention, opening two diamonds to show a minimum hand with four spades and five hearts. North inquired with two no-trump, learning the exact distribution of his partner's hand. Now knowing that his diamond-loser count had shrunk from three to one, North used Blackwood before settling South into six clubs.
    If instead the auction starts one heart — two clubs — three clubs, it might continue three spades — four spades — six clubs (or four no-trump first). Then East would surely lead a top diamond, after which the contract should make. Declarer (North) ruffs his two diamonds on the board, scoring three spades, one heart, six clubs and those two ruffs.
    But West knows about the potential for diamond ruffs, so makes the brilliant lead of his singleton trump. Now, with this layout, the contract is unmakable, assuming that when East gets in with his diamond king, he plays another trump.
    Try to anticipate the play during the bidding.