A i) 9-7. It is well worth the sacrifice of a 15 to put two near cards in your crib and leave your hand with a four-card run which must improve from two to six points, regardless of the rank of the starter.
ii) 7-A. Wide cards to the opponent, with a score of five and improvement of from one to seven points sure unless starter is a 7.
Q with Q-9-7-6-4-2?
A i) or ii) Q-7. This leaves you with two 15s, a fair chance to improve and a reasonably flexible hand for the play.
Q with Q-J-10-9-6-6?
A i) 6-6, leaving both hand and crib best chance to make a big score.
ii) Q-6. Balking cards, leaving you a score of 5 and a fair chance to improve with favorable starter.
Q with J-10-7-4-4-A?
A i) J-10. Dealer can afford to sacrifice a 15 to put two near cards in his crib, expecting high-card layoffs.
ii) 10-7, leaving you a 6-point score. While J-7 would be wider, the chance to score a point for his nobs is well worth the slight additional risk.