Some of this will just be good ol' common sense and politeness.
Not all of these fall strictly under the category of "bridge ethics," but none of your opponents will like it if you:
1) Come to the table dressed like a bum.
2) Come to the table reeking of strong perfume.
3) Come to the table smelling like you never take showers.
4) Chew/pop gum.
5) Snap cards (or play them in any obnoxious way).
6) Delay the game by:
a) Postmorteming before the round is complete.
b) Writing in your scorecard when it is your turn to bid or play.
c) Doing anything (scoring, commenting, day-dreaming) that holds up the game when it is your turn. [Don't mix this up with THINKING -- which is always allowed if you have a bridge reason to think.]
7) Call attention to a bid or play by making it in an exaggerated manner. (Example: You signal with the 9 and want to make sure partner sees it--so you leave your finger on it just an extra few seconds before turning it over; or worse, make eye contact with partner before turning it over). If your bid is alertable and partner isn't alerting, don't give the show away. Act calmly. Don't stare at partner or draw extra attention to your bid with a stare or dazed look!
8) Fumble with the bidding box. Decide on your call, then reach into the box and make your bid. Don't let your fingers "hover" over the bidding box.
9) Criticize your partner or even worse, the opponents. If you have nothing nice to say, don't say anything at all.
10) Hold your finger on your played card extra time so partner will see it.
For more, please read this article on appearing professional.
For a PDF of this article, click here.