You find yourself in 4S after opening 1C with no opponent bidding. The opening lead is the DQ. How do you plan the play? Does this change if the opponents double your 4S?
The first part of planning the play according to Kelsey is to consider the contract and the impact this has on your goals for the play:
"You are in the par contract and it is likely that most of the other declarers will also reach it. It only remains to decide how many tricks will suffice for a good score.
At IMP scoring you would look for the safest way of making the contract, and a good safety play is available to guard against a 4-1 trump break. Cash the ace of trumps and then play on clubs, allowing the opponents to make three trumps but no more tricks.
At pairs you cannot afford this safety play, since eleven tricks may be made when trumps break 3-2. The 3-2 break has a frequency of 68% against 28% for the 4-1 break. The odds are good enough to justify the risk of defeat, so you set your target at eleven tricks.
The best line is to duck a trump at trick two, ruff the diamond return, and cash the ace of spades. If both opponents follow, you will switch to clubs and rake in your eleven tricks.
Had either opponent doubled the final contract there would be two good reasons for thinking again. Not only would there be a strong indication of a bad break in trumps, but there would be no need to strive for overtricks to ensure a good score. The double should therefore persuade you to make the safety play of the ace of spades at trick two."
From HW Kelsey Matchpoint Bridge (Faber Paperbacks, 1979), p41.