Trump leads against two suited hands rank to be very effective. They are the most effective when the hand that is short in trump has agreed to the trump suit under duress, the partnership has languished in a part score, you have meaty cards in the second suit promised in the bidding and the tapping defense is out of the question.
So let's go through an example. You open 1S (AQ432, K5,87, KT97) and lefty overcalls 2N for the minors. Your rho bids 3d and the auction stops there. You expect the dummy cards to be some type of two suiter in clubs and diamonds. Those clubs of yours are going to score if they can't be ruffed in the declarer's hand and due to the nature of your partner's pass, a tapping defense is unlikely. Lead trump.
Here's another example. Rho opens 2D Flannery showing hearts and spades. You pass holding KJ95,A43,Q543,J6. Lefty bids 3H and the auction stops there. The last thing you want to happen is for your spades to be ruffed out in declarer's hand. Lead trump.
There are lots of auctions like this where you will find
- Two suiter promised either in dummy or declarer's hand
- The non length trump hand has not aggressively supported the trump suit
- Part score contract meaning the defense has values
- Tap suit is not indicated or works as well as trump leads.
- You have meaty cards in the promised second suit
Here are some "automatic trump" leads for me considering the above qualifications are met.
- 1N 2C, 2H all pass. Dummy has three suits and shortness in clubs. Lead trump
- 2D flannery .
- 2D showing a 4441 hand
- 1N 3H showing invitational in majors
- 2 level preempt, new suit by responder and raise by opener. You know opener is 6/3 at least and short in other suits. Lead trump
- Auctions that start with a TOX. Most of the time dummy has shortness in the opener's suit so why not start pulling dummy's trump?
- 1n in the hot seat usually denote week two-suiters.
- Two level overcalls followed by 2 NT show 6/4 two suiters although not necessarily weak hands.
Don't forget auctions where two suits are bid outright as opener (1S 1N!, 2C 3C) or where two suits are bid naturally as overcalls. Envision the ruffs in the non-length-trump-suit hand and go for the trump leads to prevent that offense.
I once led trump against a strong jump shift auction against a vul game score at imps. We happened to beat it at our table! WIN!