Respect the audience. Treat them like adults. This means, among other things, assuming they know how to take appropriate notes and that they don’t need a “guiding voice” in order to figure out your message.
Make your message comprehensible. This means having a central thesis and giving presenters useful guidance.
Do not try to induce socialization with gimmicks.
Run on time.
Nobody really cares about the swag. Put more effort into talks and less into stuff.
Sponsors can be important sometimes, but don’t let their interests override those of the audience, who are giving the most precious resource of all: their time.
Avoid videos.
If someone offers you candid feedback and you call them, assume that you are going to get….candid feedback. Imagine that.
This post is only here because I attended a godawful conference last week, and thought it might pay to state the obvious for others to read.