I’ve attended several hundred events and organised loads too.
Here’s a few tips about how not to do it:
Don’t create a hashtag for the event
If someone in your audience starts one for you when they ask if you have one and you say “no, but feel free to create one”, don’t tell anyone else at the event that one has been started and what it is
Ensure that all your speakers are male, and white
Don’t arrange for wifi to be available – after all, everyone has 4G on their smartphones and they want to pay to use it up at your event
If there is a microphone, don’t pass it around the audience when they are introducing themselves until half-way through the event,
If someone then says they don’t need it because they’re loud enough, don’t worry about anyone who uses hearing aids and can hear better when people use a microphone