I was at a Chamber meeting last month when a couple rules were broken that took away from the speakers' credibility.
Rule #2, This is one that drives me crazy. DON'T LEAVE THE SPEAKER'S LECTERN EMPTY. EVER! Correct speaking etiquette calls for the emcee to introduce you, stay behind the lectern to welcome you to the stage. Then at the end of your talk, please wait for that person to return to relieve you of your duties at the lectern. Never, ever, should the audience be sitting there looking at space. This rule is broken all the time. You can watch for it now.
Are there any other miss-steps that you have seen speakers make?