Most players realise that they can't say during the auction : "I don't know what to do." or "I hope that's right." Even sighing or frowning is sending a message to partner. Or waving your pencil in the air. Or full-stops after bids.
A long hesitation can also show doubt - "I have options and I'm not sure which is best."
This behaviour is not illegal under the Laws of bridge. Bridge is a thinking game and you are allowed to stop and think. BUT it is illegal for your partner to take advantage of a hesitation.
Law 16B Extraneous Information from Partner
1. Any extraneous information from partner that might suggest a call or play is unauthorized. This includes remarks, questions, replies to questions, unexpected alerts or failures to alert, unmistakable hesitation, unwonted speed, special emphasis, tone, gesture, movement or mannerism.
(a) A player may not choose a call or play that is demonstrably suggested over another by unauthorized information if the other call or play is a logical alternative.
(b) A logical alternative is an action that a significant proportion of the class of players in question, using the methods of the partnership, would seriously consider, and some might select.
What this means is that if your partner hesitates (or sighs or frowns etc) then you have to make every effort to ignore partner and still bid based on the merits of your hand. If you don't, the opposition may call the Director who may adjust the result.
Some people think this means if your partner hesitates you have to Pass. Others think they can bid whatever they like and let the opponents complain. Neither of these views are correct - the truth is somewhere in the middle.
Law 16 - Unauthorised Information
Law 73 - Communication, Tempo and Deception
Example 1 :
West North East South
1H 1S 3H 3S
4H Pass* Pass ? * 5 seconds hesitation
A competitive auction. North hesitates before passing, suggesting that they might push on to 4S, or possibly double for penalties. South now has to make their normal bid. If they would normally Pass then they should Pass. If they feel they have a little extra points and/or shape then they could bid 4S. Doubling here is a grey area, are you doubling for penalty or to allow partner to bid 4S ?
Whatever the outcome, East-West have the right to call the Director after play.
Example 2 :
West North East South
1NT Pass* Pass 2H * 8 seconds hesitation
Pass 4H Pass
West opens 1NT (12-14) and North hesitates before passing. South bids 2H on a hand with six hearts but only 8 points. North turns up with 15 points balanced ! 4H makes for 620.
The Director is called and after consultation and polling changes the result to 1NT -2 for -100. Basically the 2H was disallowed. (this occurred in a tournament)
Example 3 :
South is Declarer in 4S. South wins the diamond lead and leads a heart towards dummy's Q52. West pauses before playing a low heart, East winning the Queen with the Ace. The pause has strongly suggested that West has the King of hearts. East must try to ignore this information.
Example 4 :
South is Declarer in 4S. South wins the diamond lead and leads a spade towards AJ43 in dummy. South has five spades to the King, and has a choice of finessing or playing for a 2-2 break.
West hesitates before playing the 6 of spades. South assumes West has the missing Queen and finesses the Jack, losing to East's Queen. Spades broke 2-2 all the time, West had 65 of spades and had no reason to hesitate.
This would be ruled under Law 73 - Communication, Tempo and Deception. The Director would probably give South an extra trick.
Advice :
Try to do your best and not hesitate in the bidding and play.
Less experienced players will be hesitating all the time. More experienced players are expected to behave themselves.
A very quick Pass is also poor behaviour. It shows partner that you have a weak hand. Even with a very weak hand, always try to take a second or two before Passing.
Apologise if you hesitate. This recognises the issue to the opponents.
STOP cards are no longer in use in most places.
Try to anticipate what you are going to bid when it is not your turn. If you have bid your hand then you are going to Pass. If you have extra features then you're probably going to bid again.
Think about what call you are going to open the bidding with. But also think, "what will I do if my right-hand opponent opens 1C ? 1S ? 1NT ? 2D ? "
Check the vulnerability when it is not your turn, this may affect a competitive decision.
If you wish to ask about an alerted bid by your opponents, the question and answer do not count as a hesitation. But asking about a bid just to give you time to think is unethical.
Some players always hesitate after a jump bid by their right-hand opponent, and also after a 1NT opening bid by their right-hand opponent. This is good practice but not required by the laws or regulations. If you're going to do this, always do it.
It is normal for Declarer to pause after dummy goes down, to consider the auction, opening lead, number of trumps, and to make a plan.
Try not to pause in the middle of a trick. The best time to think is when you win a trick.