Should you hold three trumps with two honours, headed by the ace king, the king queen, or even the king jack, you are reasonably sure of two tricks in the trump suit—as can also be said of four trumps with two high honours. Indeed in the last combination, with the third best card an eight or better, there are probably three trump tricks.
With four trumps including three, or five trumps including two honours, provided the suit is headed by the ace or king, you can reasonably expect to secure three tricks in the trump suit.
Aces and kings in the side suits are usually good for a trick each; but allow for the length of the suit, the shorter it is the less probability that your honours will be trumped. It is not safe to count on making your queens; they may be classed as doubtful tricks.
Spades may be doubled with four tricks. To double hearts, diamonds, or clubs you should be sure of five tricks.
THE LEAD WHEN PARTNER HAS DOUBLED
A double by your partner indicates some strength in trumps as well as in the side suits. It does not necessarily imply a desire to get the trumps out, nor should you invariably lead trumps when your partner has doubled; your play must be influenced by the general character of your own hand.
If you hold a short suit it is obviously a better lead than trumps. You may be able to ruff with your small trumps.
It is also bad play to lead trumps up to the maker. This would place your partner’s high cards in a position to be easily captured by the dealer.
When dummy is the maker, the trump lead from weakness through the strong hand gives your partner the advantage of position; but it is safer play to win the first trick, if possible, and decide on your subsequent play after seeing the dummy hand.
Avoid leading trumps to your partner if you hold the ace, the king, or the queen of trumps guarded; your partner may have doubled on high suit cards with but little strength in trumps.