This is an excerpt from the book "Bridge; its Principles and Rules of Play" (1906) by American expert J.B. Elwell. All of the rules are still relevant over a hundred years later!
There is nobody who cares to be told that he plays cards unfairly; but, if you permit your manner to give your partner or the opponents the slightest intimation of the cards you hold, you lay yourself open to such criticism. Cards do not carry with them a license to be unfair or rude, yet, at the Bridge table, many socially correct people are both.
- Try always to pause the same length of time before making the trump or passing. Do not allow your manner to express approval or disapproval of your partner's make or of the cards he plays, and select each of your own cards with equal deliberation.
- When you hold good cards be content to win tricks with them, without manifesting glee at your adversaries' defeat.
- When your cards are poor, do not complain of them; you imply that the opponents profit by your weak hands and not by their own skill, and, as a rule, the more you rail at your luck the worse it becomes.
- Be generous with your praise of a well-played hand, and be sure your partner will play a better game if he does not fear your adverse criticism.
- Do not permit yourself to take advantage of, or be deceived by, any mannerisms of your partner or of the opponents, and let your own manner be uniformly such that nobody can tell from it whether you are winning or losing.