Signals

 The backbone is that it is easier to DISCOURAGE ONE suit rather than to signal for a PARTICULAR suit!

 The most obvious and fastest approach to proceed with a suit preference signal (SPS) is the Best Trump Signal (BTS).

 Let me first give an example to set out the foundation of  BTS.

 For the purpose of the discussion let assume that the opponents are playing in a heartscontract. Partner leads a suit (so far ANY, even perhaps a trump!), you see dummy, and you hold something like 862 in hearts. Further on let suppose the declarer wins the lead (Don’t forget to show preference whenever possible!), draws trumps in either ONE, TWO or THREE rounds.

 What are your options?

 On the first round you can play any of the three hearts you hold.

1. You play 2. The message to your partner reads as follows:

 “For the time being I have no interest in you playing spades, when or if you regain the lead!”

 Mind that spades are the highest ranking side suit and 2 looks like a very small card.

 Your decision can be based either on holding nothing in spades, or an urgent need for partner to lead another suit (so far not exactly specified whether clubs or diamonds), or to deceit the declarer with those assumptions.

1. You play 8. Hopefully partner can deduct that this is a fairly high card, i.e. at least TWO lower cards, 6 and 2, are missing. The message is practically the same as above. Just swap spades with clubs.

1. You play 6. The message now is not as informative as above. You plan to start an ECHO, that is, you will clarify your intentions later, when playing a SECOND card.

Let’s see what happens when or if declarer draws a second trump.

If you had first played 2 (Case 1), now both 8 and 6 (LOW-HIGH) confirm the initial message (“I don’t want spades!”). You should plan to start an ECHO, so that on a third round of trumps to specify either diamonds (the higher ranking suit) with the sequence 2-8-6, or clubs with  2-6-8.

The same considerations apply to the play of 8 on the first round (Case 2). Since your other hearts, namely 6 and 2, are smaller (HIGH-LOW), you just instruct partner to avoid playing clubs. You should plan to start an ECHO, so that on a third round of trumps to specify either spades (the higher ranking suit) with the sequence  8-6-2, ordiamonds with  8-2-6.

In Case 3, first playing 6, you must finish the ECHO. 8 (LOW-HIGH) discouragesspades. Alternatively 2 (HIGH-LOW) denies clubs.

At a glance there is a contradiction. Case 3 looks dormant if you can send the same message, “I don’t want spades/clubs!”, as in Case 1/2. The main difference is that the other cases tend to be more imperative than advisable, while Case 3 is clearly more flexible.

Finally, when or if the declarer draws a third round of trumps, you can comfortably finish the ECHO.

What happens if you have two trumps only?

Basically it’s the same case. On a third round of trumps your discard finishes the ECHO.

N.B. When you have already signal for a specific suit, the 1^st time you play to that suit is used to show length, i.e. ODD or EVEN number of cards in this particular suit.

Summary

• You start the defensive play by indicating a suit you have no desire for partner to attack when on lead.
• HIGH-LOW trump play discourages the lowest ranking suit, while LOW-HIGH the highest ranking one.
• On a third round of trumps you may show either length in a particular suit or finish an ECHO for the better promising suit partner is advised to attack when on lead.
• BTS can be applied for NT contracts. Consider the main suit of the opponents (usually longest) to be the trump suit! 
  

The same principles can be used throughout the defensive play. Just watch what cards partner plays in immaterial suit(s). If it’s a pattern of HIGH-LOW the preference (“I have something!”) is for a higher ranking suit. Logically, a pattern of LOW-HIGH indicates some value in a lower ranking suit. 

Certainly, with no values in any suit partner must break the pattern so that not to give false expectations!