When the dealer takes up the trumps before the play begins, it is his duty
to discard or reject a card from his hand in lieu of the one taken up. We
will suppose that the ten of hearts has been turned up, and the dealer
holds the king and Right Bower, with the ace and nine of clubs, and king of
diamonds. The proper card to reject would be the king of diamonds. There
would be no absolute certainty of its taking a trick, for the ace might be
held by the opponents; whereas, retaining the ace and nine of clubs, the
whole suit of clubs might be exhausted by the ace, and then the nine might
be good. If the trump were one of the red suits, and the dealer held three
trumps, seven of spades and seven of hearts, it would be better for him to
discard the spade than the heart; for, as the dealer's strength is in the
red suit, the probabilities are that the other side will be correspondingly
weak, and the heart would therefore be better than the spade.
Where you have two of one suit and one of another to discard from, always
discard the suit in which you have one only, for then you may have an
opportunity to trump.