We recommend using an in-meeting survey, sent out 5 minutes before the end of your event.
Create a survey to get feedback on how the meeting went, whether the presenters were good and whether they'll recommend things to their friends.
It's important to turn that survey on before everyone leaves, while the meeting is still gathered. Make the last 5 minutes of the meeting about that feedback survey. It’s often helpful to let people know you have a silly, competitive poll after the final survey (like “which is the best sports team”). This encourages them to fill out the survey so they can move on to the next question.